Shield block every 5 seconds while using: Shield Slam every 6 seconds, Revenge when possible, and Devastate in between those. Throw in Heroic Strikes to dump rage when over 50.2) What sort of cycle would you use to generate threat, assuming you need to use Shield Block?
Nope, just critical strikes.3) 490 defense makes you immune to crushing blows?
Nope.4) 25% block chance is required?
Achieve 102.4% combined dodge/parry/block/miss.5) How can you become immune to crushing blows?
It can be. It adds 0.04% dodge/parry/block/miss, so it will improve your avoidance by 0.12% per point, as well as increasing your block by 0.04%.6) Is it useful to build Defense past 490?
Sunder Armor costs 3 less rage assuming you have a maximum efficiency talent build. However, Devastate will cause more threat after you reach a certain amount of weapon damage. I believe its 301 threat from Sunder, and 101 innate threat from Devastate. Assuming those are correct, if your Devastate does 200 damage, you are doing the same threat from each, while adding damage/chance to crit/weapon procs. Of course you could factor in the rage difference, but if you have King's Defender or equal, you should be doing about 250-300 Devastate damage, so then Devastate is more rage efficient anyway.7) Devastate and Sunder Armour: Compare and contrast
It's a good idea to have a set of gear with lots of avoidance. It's very useful on bosses that attack so fast that you will need to avoid attacks to reduce the odds of getting hit without Shield Block up.8) Is it a good idea to stack a lot of avoidance in your gear? Why or why not?
However, in normal gear, I advise against stacking avoidance. You will get less rage, and have less health and armor. If you are working on new bosses where you need to survive their reliable burst damage, if you have bad luck you could obviously die. You threat generation will suffer if your avoidance is too high as well due to not getting enough rage from incoming hits.
It's also arguable that it makes little difference in most situations due to constant heal spamming making it pretty moot if you avoid normal attacks or not. It's also considerably easier to judge what rank heals and what interval to use while healing if the tank is taking constant damage, rather than having streaky damage.
As for questions, the best I can think of at the moment would be asking things such as what upgrades they currently want. Perhaps explain why they would value the upgrades over their current gear. Have them include upgrades for all tanking sets, so you could see if they value an avoidance set and a threat set and what their itemization in those would be as well.