I'm very late to the party, but having recently finished the novel, and with the DVD is still a month or so out, I thought I'd add some details from there to fill in the gaps from the film. I haven't seen the film yet, so I'm not 100% sure about where they may conflict.
*Planetary shield.
Starting off with the shield over Scarif, in the novel at least, the shield is definitely still up after the ISD crash, only the gate itself was opened. A big difference though, is that in the book the wreckage evidently struck the shield inside the ring, rather than the station itself, essentially popping it like the film inside a bubble blowing ring. It's also stated that the shield would "regenerate swiftly enough." A key plot point was that the Mon Cal vessel had to park right over the open gate to receive the transmission. If the Profundity was vulnerably parked right over the wrecked gate in the film, I'd guess there was still remaining shield coverage that prevented them from maneuvering elsewhere.
Other points regarding the Scarif planetary shield indicated that it was fairly robust, considered a "hardened target," certainly enough to protect the planet from any conventional attack they might have expected from the rebels at that time, with the planet's commander stating that the gate itself was the only weak spot, and that "massive amounts of firepower" could penetrate it. The Rebel admiral also determined they wouldn't be able to crack it in a reasonable time with the ships they had, (why the ion torps wouldn't have worked is beyond me). Also, the shield itself was evidently considered a significant asset, the loss of which Tarkin specifically took note of, along with the Citadel itself, before firing on Scarif.
*Death Star firepower.
It is confirmed that the D.S. S.L. employs multiple kyber crystals. There were also a number of technical sidebars and *intercepted memos* that lay out a lot of technical details about the D.S., as well as a description of the beam's composition. Here's a portion starting on page 105:
From the focusing dish on the station’s outer shell, the beams of light and charged particles poured into a single vertex controlled and suspended by the kyber fields.
...
the last stage was triggered: From the center of the focusing dish came another particle beam, invisible to the human eye. It carved through the nexus and tunneled a path for the energy’s release, funneled the conflagration away from the battle station
The D.S. was also intended to be able to engage hostile fleets as well, on page 58:
The battle station is certainly not symbolic, meant only to demonstrate the Empire’s might in ceremonial planetary executions. The main weapon must be built to fire repeatedly within a short span, as it might during the course of a single fleet battle.
Later on page 179, a sidebar memo reveals Erso's manipulations to install the exhaust port vulnerability, it's indicated that even with the vent, some radiation leakage would cause health risks for low level personnel if the weapon was fired 3 times within an hour. That doesn't indicate a particularly high rate of fire, but isn't a hard ceiling either. It also gives a clue to the level of efficiency of the main reactor, though I should note they evidently possessed some kind of "particle funnel and recycler" technology that supposedly would have done the job better, but timetable overruns helped Erso nudge the bureaucracy into taking the quick and easy path, including the "shoot here to blow me up" hole.
As for the firepower, there are some specific details that could possibly shed light on the power/nature of the weapon, but many of the descriptions are muddled and inconsistent. Regardless, it almost certainly should put a major dent in the ICS numbers. While the low yield shot was considered "unspectacular at best" by Krennic, wanting to show off his toy, it was also clearly indicated on page 122 that the Jedha test demonstrated that "the Death Star might destroy a city or a rebel base unimpeded by planetary shields or defense grids." It's also pretty obvious this level of yield should 1-shot a cap ship à la ROTJ as well. Also, on page 238 Tarkin reflected that he had "half expected every nonessential system on the battle station to burn out after the test on Jedha." - and still wasn't entirely confident it would completely obliterate a planet.
*Stormtrooper armor.
Cocytus wrote:
I am continually amazed at just how worthless Stormtrooper armor is.
....
And it all seems to be uniformly useless against absolutely everything. Blaster rifles, blaster pistols (I'd expect Han's is well above spec given his line of work, but even so) swung rocks and now firmly established, kinetic impacts from Chirrut and Jyn's staves. Am I overreacting here? It's just comically worthless at this point.
Yup, I don't see any way stormtrooper armor can be argued to be "good" here, though I wouldn't go so far as to call it comically worthless. The way I figure it, stormtrooper armor should fit under the "some protection is better than none" category. I imagine the bodysuit/plates/mask would better allow a trooper to continue operating under harsh battlefield conditions filled with hot flames, choking smoke, flying debris etc. The problem is
Hollywood already grants that kind of resilience to everybody, so it only really grants mooks a bonus toward realism in shrugging off ill effects that the heroes can do naturally. Having said that, the novel made a few halfhearted attempts at implying the armors value... but admittedly ends up doing even more damage to it's usefulness.
Early on, Cassian uses a blaster with a silencer that diminished it's power enough that he was concerned it may not fully penetrate the armor. Of course it did work, flawlessly, so big whoop. Much later on Scarif, the initial rebel ambush indicates that the armor didn't even protect well against shrapnel, tinnitus or disorientation from nearby blasts. Of course, these were from demolition charges, not flash bangs, it could be argued that without the armor they'd have actually been dead, or permanently blind and deaf. Still, it's not rocking my socks off. Here's the relevant quote from page 250:
For the better part of five minutes, the rebels held the advantage. The stormtroopers who survived the initial detonations were stunned, deafened, blinded, injured by the blasts and thunder and shrapnel.
On the plus side, it's indicated that the helmets at least have better than simple tinted lenses, specifically including an automatically adjusting light filter, and possibly integrated IR sensors, though the latter could have been indicating the use of hand held scanners. From pages 108 and 169 respectively.
*Fighters.
On page 163, the ordinance that struck the landing pad on Eadu, ultimately killing Galen Erso was identified as a proton torpedo. I'll note now that arguments could be made that Blue Squadron was holding back, dialing down the firepower, as the novel does indicate on pages 158-159 that the fighters were informed of alliance operatives on the ground, but it was too late to call off the attack. Even so, it doesn't bode well for high end firepower figures. Then there's the fighters striking the landing pad, yet failing to disable Krennic's shuttle just sitting there? The whole attack was a fiasco from whatever angle it's looked at, from firepower to planning to execution.
One point about the TIE brought down by a hand weapon. In the novel at least, it wasn't destroyed outright, but was instead caused to crash, I don't know if that's a contradiction or not. Either way, the novel does specify that it was Chirrut's "light bow" that brought it down. If they're playing it as a class of weapon like Chewie's crossbow in TFA, that could indicate something more than the typical blaster rifle could accomplish. It also indicated that Andor was impressed by the weapon's performance. In the end I doubt it makes much difference though, seeing as how the Rebels cartoon already had an E-11 put a hole in a parked TIE's fuel tank once, and recently had a well placed pistol shot at point blank range force a shuttle down. Eh.
*Space combat.
The effective range of starfighters would appear to be significantly less than than 50,000 km. No surprise there, but it's the first time I recall ever encountering such specific figures for Star Wars. The scene is ambiguous enough that capital ship combat ranges could still go either way. I'm sure nothing remotely resembling this distance was seen in the film, but it might be useful at some point in the future. Here's the relevant quote from page 265:
"Withdraw to fifty thousand kilometers from the shield gate,” Raddus said. “Stay in the TIE fighters’ range but force them to stretch their line. If they don’t think to regroup, the point-defense gunners can handle the bulk of them."
The Imperial forces over Scarif (and the rebel's detection abilities) are detailed as follows:
The Profundity had detected— and its crew or its allies had visually confirmed— two Star Destroyers, at least nine distinct TIE starfighter squadrons, and innumerable midsized vessels ranging from shuttles to patrol cruisers, all situated between the rebels and Scarif. Other enemy craft, as yet undetected, could have been hidden behind planets and moons or running dark on auxiliary power.
It's implied that the TIE squadrons noted did not include those still docked in the shield gate.
There are a lot of little tidbits regarding the space battle in the text, overall it paints a picture of more complex engagements than just "shoot until the shields fail," but rather something of a jumbo sized dogfight with a lot of dancing around and jockeying for position. Essentially the weaker rebel fleet used superior numbers to keep "the Destroyers boxed in, unable to turn their full firepower on one target without exposing a flank to concentrated volleys." This scenario played out twice. Once when a hammerhead corvette somehow let itself get caught between the 2 ISDs and was forced to withdraw to the rear (this would later be the ship sacrificed in the ramming maneuver), and again when an ISD let itself get flanked on both sides by capital ships, leaving it's forward arc open for the Y-Wings to make their ion torpedo run. This description implies greater complications than simply having magic ion torpedoes to throw at a target, and possibly why they couldn't just use them against the shield gate.
All in all, it doesn't paint a very clear picture of their offensive or defensive systems, other than "it's complicated." But heck, even without gigaton turbolasers, the nature of Star wars space combat has been muddled and confusing all along, so I'd say it's really par for the course so far. Also, those ion torpedoes must have some other drawbacks, they seem way too overpowered based on the brief use here.