I have one question for every single one of you in this thread. Do you even tank?
I highly suggest that you take less endurance. As a vanguard/powertech tank who already needs the most amount of healing (by a small margin) you're worsening your situation by trading average mitigation for endurance.
Hardmodes let you get away with a lot (and that's a good thing since it encourages more to try them!) but now you're overgearing an operation so you can get away with a lot.
Oh and to the OP, 43-45k health is normal for tanks in 78 gear even without high endurance and endurance augments. Mitigation 78 will get you above 44k health (although I get 3% as an assassin so for other tanks it can be 43k). On the other hand I've seen dps with over 40k health please stop whomever you are.