You're getting a job trait you have performed exceptionally without for 13 years. You're looking a gift horse in the mouth here, PLD doesn't need HP Bonus, and frankly I'm surprised they're even getting 2 traits.

While you're right about those jobs being better DDs, PLD has a desirable place in endgame right now, maybe not in all events, but right now they're good. They're in a place were they're needed. I on the other hand, have never seen a shout for NIN or RUN... and MNK is only a superb tank because of its high HP... giving RUN and NIN the high HP of MNK might make them at least acceptable in some events. That said, IDK bout WAR... perhaps it was because WAR was the original tank job, maybe they're trying to make WAR on par with MNK in terms of HP so they're as desirable as a DD tank in those situations.

I don't have the answers for everything, but I do have the answer for why PLD only got 2 traits. They don't need it. Maybe WAR didn't either, but NIN and RUN did.