TBH I'd love to go back to smaller numbers. I remember back in TBC, seeing a tank with 20k HP and going "HOLY SHIT THAT TANK HAS A FUCKTON OF HEALTH". Or seeing that I had 7k mana and thinking that was a lot.
And really, right now in Cata, it feels really awkward...the gap between 1 and 85 is gigantic. Going from 300 hp at level 10 to 160k at level 85. Whereas back in Vanilla, 1-60 felt somewhat balanced in terms of numbers, going from 300hp at level 10 to 4k hp at level 60. (no, I am not a vanilla fanboy.)