Just my opinion here, but if you play your cards right while levelling, then Haxorus can retain his godly attack while have a decent amount of defence. Also, I tend to swap him in against anything that isn't dragon or ice, just call me paranoid.
So anyway, I gave mine a quick claw. This way, he might hit first every now and then. This, along with his swords dance makes him unstoppable.
Honestly, at level 64, EV training a good hydraigon is hard, because the first 2 evolutions, well, like all dragons, ARE WEAK AS. so honestly, in my opinion, HAXORUS.