You're conflating effective hit points with required healing (i.e. mean mitigation). PLD and WAR have effectively identical effective hit points: an unmitigated attack hitting a WAR is going to do the exact same damage in percent of total hp as it would hitting a PLD. What you're attempting to say here is that WAR has inferior mean mitigation, even when you factor in the self healing that WAR gets that is intended to close the gap.
Inner Beast is actually a *very* powerful tool, allowing you to get pretty close to making up for the extra 8.7% healing that WAR is going to require thanks to the loss of Wrath stacks. The problem is that Inner Beast doesn't scale which means that it works wonderfully in 4 man content but becomes a monumental liability in 8 man content. The entire point behind it is that you have to weigh the short term benefits of using it against the long term costs. It's not *supposed* to be a tool appropriate for all situations. If it didn't have the Wrath cost attached to it, there wouldn't *be* any reason not to use it all the time, which means that it would need to be weakened to compensate.2. Inner beast is terrible. The heal is kind of meh but the worst part about it is that it removes your 15% healing buff, which means you're making it EVEN HARDER for healers to keep you alive, it's really stupidly designed.
The devs have pretty much stated that they intended for WAR to be the skill tanks and for PLD to be the faceroll tank. In the first Live Letter, Yoshi-P dismissed any player concerns about WAR as players just not knowing how to use the class properly and that they fully expected WAR, when played well, to outperform PLD. That's pretty much the definition of a skill tank. Abilities like Inner Beast are what *define* skill tanks: if you use them arbitrarily, you're going to get piss poor performance but, if you know how to leverage them properly, you get excellent performance out of them.
For Inner Beast, it's all about knowing the ebb and flow of the fights: you can safely use Inner Beast without feeling much of the effects of the loss of Wrath stacks by using it right before you know the boss is going to stop attacking you for a window. In Coil Turn 2, use Inner Beast right as the other tank is about to pull off of you, since you can easily get those Wrath stacks back while your own stacks are fading. On Titan, you can use Inner Beast right after the even Mountain Busters without any issues since he proceeds to spend the next 15 or so seconds on Weight of the Land and gaol, which means that all that's hitting you is the 1 auto-attack he throws at you between using the two.
Inner Beast is bad (in 8 man content) because it doesn't scale like static mitigation (so that it becomes effectively worthless on any fight with more damage than your average 4 man boss fight), not because it has an opportunity cost. If you removed the cost, you'd be removing the "skill" aspect from it, which is counter to the intent of the class.