Now I'd like to preempt this by saying I'm happy WAR is getting some love. It's always been and always will be my main. It's had some pretty glaring flaws since day 1 (as has every class in some form really) but I'm gonna go against the grain here and state that we've never been in a bad spot like others might claim. I've tanked absolutely everything this game has to offer without any issues and whilst it's clear to everyone we have less potential mitigation (in very high damage situations) than a PLD that is absolutely not a problem. The class has more than enough tools to handle tanking everything up to and including Twintania as is.
Anyone who has spent any reasonable amount of time on WAR should pretty easily be able to point out some of the real issues the class has. Holmgang has exceptionally niche usage (resisted by almost everything worth mentioning), Storm's Path was completely useless, Steel Cyclone had very minimal use and Vengeance served mostly as a free stack of wrath rather than a functional buff. There's other minor stuff I could touch on like Bloodbath, but none that really require any noteworthy changes. I'm really glad to see these all receive buffs (Steel Cyclone still needs love, enmity was not the answer), though I think some are a bit overkill. I just wanted to touch on these before getting in to the discussion of Inner Beast to give some perspective.
Now here's my beef - the complete retooling of Inner Beast. Though some may disagree, Inner Beast is the central focus of a Warrior. The entire class and playstyle essentially revolves around Inner Beast; how you manage and build wrath, when you pop it and a number of your cooldowns (Berserk, Internal Release, Infuriate) all involve or lead up to Inner Beast. Proper usage of Inner Beast may be the most defining thing between a bad and a good Warrior.
That said, there's a lot of controversy behind the skill. Misinformation surrounding it spread like wildfire and it became common practice for a WAR to sit comfortably on his/her 5 stacks of wrath, refusing to use them unless Infuriate was available. To put it simply, you are bad if you play like this. Remember when Yoshi-P came out and stated the community was playing WAR wrong? Everyone laughed it off, called him crazy and refused to accept it. The fact of the matter is he was absolutely right. It may not encompass everyone, but the grand majority of Warriors followed this line of thinking despite it very, very rarely being the best way to play. This style of play, higher baseline gear requirements (and lack of CT tier as a bridge) for the class and PLDs ability to scale DR well with content (regardless of gear) absolutely destroyed the communities perception of WAR, despite the class being a very good tank that synergizes very well with PLD in 2 tank situations.
Now I'm going to use Titan as an example here because I imagine it's what most people have experience with, it also seems to be the first real case of people favouring PLDs and writing off WARs entirely. If you haven't reached Titan HM you honestly shouldn't be engaging in any balance discussion, each class is equally good regardless of gear prior to Titan.
Inner Beast is currently used to proactively mitigate damage. Now this can be done one of two ways, either via buffering your HP just before taking a big hit or healing it back quickly after it connects. In an ideal world it will always be the second option, but there's situations where the first is necessary too. When I hit Titan HM I could be healing from anywhere between 1000-2250 or so, with current gear I'm up to 1300-3000, with BIS you can push that to around 1500-3400 (I'm discounting STR+15 accessories and 30 STR allocation but they're an option too). As you can see that's a huge chunk of mitigation, with the option of using it before Mountain Buster connects in an emergency or shortly afterwards (timed carefully alongside heal(s)) to top yourself off. This is really where WAR differs from PLD. With the upcoming changes in 2.1, Warrior is shoehorned in to thinking and playing like a Paladin. You will pop Inner Beast before MB each and every time, healing around 333-750 (500-1200 with BIS) and reducing the MB by 20% damage. At a base level this is slightly more mitigation overall, but in cases of Berserk + Crit (not uncommon with Internal Release) it is a bit worse.
So why am I complaining? The biggest issue for me is loss of identity. No longer do we have to decide the optimal timing to use Inner Beast, you will be popping it just before Rock Buster each and every time. This is exactly how PLD plays (though with more leeway on the timing, with buffs ranging from 10-20 seconds over IBs 6). No longer do we have to have to pay any attention to our healers actions or worry about precisely timing it to minimize lost healing potency, we blindly pop it before the scripted burst damage and go back to our combo rotation.
It's also a big nerf to Infuriate. You're down to one healer, they get locked in a gaol and in just a few seconds Mountain Buster is coming your way, what do you do? A quick Berserk followed by a double Inner Beast and you're back up to full HP just in time to eat the MB. Your healer may need some new underwear but the fight will go on and damn will you feel good about it. Say good bye to situations like these (and I'm sure nearly every tank out there has been in a similar situation at least once), because double IBs are now near worthless. You can prolong the 20% DR to 12 seconds but why bother? Every fight with burst to worry about has downtime between each hit. You're not eating another buster for a while, Cadaceus gives you around 15 seconds between Hood Swings (hardly worthy for saving IB for anyway), Twintania has a whopping 30 seconds between Death Sentences. Wrath stacks in general require absolutely no thought now, there's no trade off to using them.
Another problem is Inner Beasts utility prior to Titan and coil. In larger AoE pulls it may be a minor increase in mitigation in 2.1, but in near every boss up to and including Garuda it will likely lose effectiveness. Whilst DR scales better in heavy hitting content it gets significantly worse in easier stuff. No longer can I shrug off Ifrits 1.6k incinerates, healing back the entirety of it, I'll be reduced to lowering it by... 320 (on top of a 400 heal). It only gets worse from there.
So what do I propose? I honestly think IB was perfect as is, the other skill fixes were more than enough to bring WAR up to par (if not ahead of PLD). It's true PLD has an easier time eating hits in Titan and coil without requiring as much gear, but the gap is not a particularly big one. As a WAR gets more and more gear the gap gets increasingly smaller. Classes should not be identical. There is nothing wrong with PLD being a bit better at soaking up hits. Warrior can put out noticeably more damage, can generate enmity faster (great for adds, turn 4, etc) and buff PLDs damage in cases where it falls back to a DPS/back up tank. Perhaps the proposed buffs alongside the old IB would be too good? In that case you should be toning down those changes, not butchering our one class defining mechanic/skill. Drop Vengeance from the proposed 30% DR to 15-20%, if Storm's Path is a 10% DR change it to 5%. There was so many routes you could have taken when fixing/buffing WAR, but instead of playing to the classes strengths and flavour you're simply turning us in to a PLD with an axe.
This got entirely too long despite trying to avoid elaborating on every point I made, so apologies for the wall. I'd be happy to go in to anything I mentioned further if necessary.