I thought bully was changed to only work with targets that were knocked down? Does it work on other status effects?
Well the new wiki says it still works with crippled/KD/slowed, but that could be wrong. It's still a huge damage increase even if it's just KD, which is a pretty common effect. I think it should work with crippled/KD/slowdown but decrease your base damage.
Oath of desecration is 40%, it also costs 3 AP. Power stance is pretty minor (only 20%) but it costs 0 AP. They all stack multiplicitively if I'm not mistaken. At release, power stance increased the AP cost of attacks by 1, which it no longer does.
20 armor is actually fairly significant because of the way armor is calculated. About the first 80% of your armor doesn't do a thing except get you up to level. Imagine you had 100 total armor and that resulted in 50% damage reduction. At 80 armor, that damage reduction might well be down to 1%, and it will stay 1% all the way down to 0. It's a really strange system they have and I don't know the exact calculations, but it means that a small increase or decrease in armor can mean a fairly substantial difference in effectiveness, which is necessary for things like iron hide or armor specialist to do anything at all.
Not that it matters if you have 0 armor when your enemy is knocked down or dead.
Anyway, they all needed adjustments and I won't say just where it would have been "right". It is however NOT right where it is now. They nerfed an entire mechanic to uselessness, but left the core problem in the form of other abilities. If they had no plans to actually fix the problem it would have been far better had they left sneak completely untouched. As it is we have one fewer mechanics to play with and the game isn't any closer to being not-broken.
Well the wiki (again, could be wrong) says the armor formula is:
Proportion Blocked = Armor Rating / ((4.5 * (1 + Attacker Level)) + Armor Rating)
Now, a lot of this depends on what the average armor you have at a given level, but this to me makes 20 armor seem not very significant at a higher level, where I assume you have 60+ armor, no?
Let's say you have 60 armor at level 12. That gives us 60 / 58.5 + 60, or 60/119 (rounded up), for almost 50% damage reduction. With rage, that becomes 40 / 58.5 + 40, for 40/98.5, for 40% damage reduction. That's not trivial, but it's not that much. Now, maybe I have the armor numbers wrong, but the only way I can see -20 armor making a really significant difference is at low levels or if you have low armor at a high level (most likely for a ranger, though I don't even know if the ability should work for ranged weapons at all anyway, or at least it should to a smaller degree). The biggest problem (besides the enormous damage boost) is probably that it doesn't scale at all.
Your experience seems to suggest this formula is wrong if you find a loss of 20 drops your resist from 50% to near 0%. You're sure small amounts of armor can make such a huge difference? If so, it really seems like the formula must be completely different.