The full drop is way too heavy, really. Wow...tried it several times on test with my 33 inv/ss, all the combos I could think of, and even with stamina and unstoppable running everything drops.
Toggle drop = death.
I didn't see the disorient as a 'useless' downside, personally. Back with just unyeilding stance (pre i3), and now with unyeilding, I've still had a Freak smasher stun me during the Rage disorient drop. At least I had endurance then, and the new inspirations you can use while disoriented are great!
I'm not sure what to suggest, but if you devs feel the disorient is too easily circumvented, I would have to say a post rage end drop is a decent idea, just not ALL our endurance, considering we are quite likely still in the thick of it when rage ends.
Or, it has to last long enough to carry us through even long fights, like AV fights. Think about it: I never intended perma-rage (I dislike relying on 'modifiers' to be effective; personal play style makes me feel they are too much of a crutch), but like to save rage for the tough guys, where I need to break out the big guns. I.e., +2 con or higher lts, or any boss post-i3, or, of course, AVs.
(btw, new invincibility feels good. Still getting hit more than in i2, with 2 def buffs slotted, but it really feels like it's noticably working, and against ranged as well as melee...no big team test, but against +1 con Crey Patrol, about 8 of them, it felt just right, taking hits, but nothing I couldn't handle)