How do you use Inner Beast Effectively?

I main War tanking have since launch but I'm a pretty casual player you can say. I only just barely finished an ilvl70 set when 2.1 launched. I haven't done coil and I only just did Titan couple weeks before patch hit. Aside from special fights like Titan where you know what big move is going to come out next like clock work how on earth do you use Inner Beast Effectively?

I don't think I was ever a great tank but I don't think I was god awful either. These warrior "buffs" make me feel like a mental retard as I fumble around with the new ability set. Everyone keeps telling me the playstyle hasn't change that I should just keep doing what I did before for the most part but I feel like everything has just flipped on its head.

And I think the core of my frustration is Inner Beast. I can use it effectively on Mountain Buster in Titan sure. But I can't for the life of me figure out how to use it effectively on say the AK final boss. Before if for whatever reason (say the healer had to run away to drop an orb) I saw my life was getting low, I could just pop a buffed inner beast and gain what felt like a significant portion of my health back.

But now to get any sense of effectiveness I have to pop Inner Beast before an ability lands. How do you do this? 99% of the time when I see the wind up animation my abilities are on global cooldown so I can't pop the buff in time. I don't know exactly when the AK boss will use rotten breath for example so how do I use Inner Beast to counter it? Is there a way to know when he will use abilities like Titan that I just have never noticed?

I tried to just pop it every time I hit 5 stacks of wrath but it seemed like the buff lasts so short it will maybe be up for an autoattack at best. Is that really the best I can do with the ability now? reduce the damage on a handful of autoattacks and if lucky an ability or 2?

Everyone wants to give me high fives over these warrior buffs and I wish I could go dancing in the streets too. But I'm an utter stress case cause I feel just so damn incompetent at my job now. I tried some dungeons and I feel so damn squishy. I can never seem to pop Inner Beast in a manner where I'm feeling like "well at least I mitigated damage to the best of my ability."

tl;dr I'm an utter stress case and can't enjoy the new content. I want to get good at my job again but I can't figure out how to use Inner Beast properly on normal joe schmoe dungeon bosses. Please help.

All bosses have skill cooldowns and skill rotations. Learn the timers for the skills and the rotations, and then you'll know when to use mitigation buffs.

for hard hitting fights like CAD in turn 1 of coil i use it on CD its built in to my spam macro for HS. Basically warrior hasnt really changed except the new debuff. I basically go HS>SS>BB then i rotate my 2 debuffs HS>maim>SE , HS>maim>SP then back to HS>SS>BB. using inner beast on CD you build it so fast its worth using on CD on hard hitting boss fights or mobs. because ability+auto attack may take you very very low.

If the boss has one thing that will hit you hard (ex: Titan's Mountain Buster, final boss of AK's breath attack, Twintania's Death Sentence, etc.) you should use it directly before it happens (preferably with the SP debuff up). Otherwise, with bosses that just constantly hit you with stuff, you'll want to use it on cooldown. Sometimes it's worth holding onto it for if you drop to half or something and need to mitigate some damage while you're getting topped up to full - but in general you'll just want to hit it when it's up. This applies to trash pulls as well. Just make sure when you use it you won't need it again before you have another 5 stacks of Wrath up, basically.

My priority list of strategies to use for IB:
1. Use before a predictable hard hitting ability
2. Use when healers is forced to move to avoid damage (or is disabled/distracted)
3. Use Off CD

Note:
#1 is fairly obvious for when these situations exist. For the most part, if a guide states to blow cooldowns for a certain mechanic, IB should always be included.
#2 is lenient but helpful for fights like Ultima/Mog/Turn 1 (low stacks)/Turn 2 (Firestream/Ballasts) where the boss will continue it's basic attack while other mechanics take place that can steal a healers attention. The logic is, if there is a situation where a healer may be forced to move, and point #1 is not in effect, then use IB during that situation. I personally will (attempt to)keep an eye on a healers cast bars and if there is ever a gap within their casts, then I pop it for more support.
#3 I'm lazy and/or the content is trivial. I also use this when damage is constant and extreme where any (and all) mitigation will help survive.

Ideally you want to use it before a high damaging ability, for example in Titan EX if you know the rotation you can pop IB before mountain busters.

However if you are unable to predict these attacks, the next best option is to use it directly after them. That way you'll get a small heal and the added mitigation will help your healers get your HP up without the following attacks killing you.

Thanks for all the replies. It looks like there are a few different strategies depending on the fight. I think I've calmed down a bit though I still feel these changes are quite the adjustment in playstyle. I'm at least not stressing about it as much. I'll try popping it on coolodown again for some fights and see how that feels. I don't think I'll ever get to a point where I can predict Rotten Breath in AK. I just don't do the dungeon frequently enough but hopefully I can make do.

Rotten Breath happens 2 times between each Imminent. One about 10 seconds after Imminent and the last one around 20 seconds before the next Imminent. But if you ask me I'd just say its just AK, spam Inner Beast however you like. Only vengeance is worth pondering over when to use.