"How good is the tier 12 2-piece set bonus? I'm a little wary of it, primarily because battleshout triggers GCD so I don't normally use it every time it's up, and because I'm not in a rush to break my 4-piece T11 bonus"
I don't think the 4-piece T11 is overpowered and unfortunately I think T12 bonuses are bad, especially for smf warriors.. You're going to have to mess up the t11 4 set eventually. I'm assuming the added strength is an upgrade. If you're lucky you will get a drop from BH and buy the valor chest (which looks pretty good stat wise)
"I need help w/ BIS trinkets for fury warrior. Currently I have equipped LTS and Apparatus of Khaz'goroth. I also have Fury of Angerforge and Heart of Rage. Which are my best options? Thanks!"
I'm pretty sure Apparatus of Khaz'goroth and the trinket from Ragnaros are BIS. If you have the heroic version of Heart of Rage I would go with that and the Apparatus. If your don't have the heroic version I'm inclined to think LTS and Apparatus are better.