I haven't hit 80 yet since I've been kind of lazy, but here are my experiences so far on grinding.
76 & 77 I mostly did in Katta missions & Fort Mech. when working on the Oil Can charm quest.
I'm 78 now, at exp is still pretty good in Katta runs. During my off times, I would work on AA's in HoH since it's a hotzone and not too bad solo.
Bloodmoon is pretty good exp too if you can get a solid fast killing group.
At 78, I found that Hills of Shade is really good exp too. Get a decent group for chain pulls and you'll get 1% about ever 2 kills or so.
I don't do much soloing, so most of my experiences are in CoA+ geared groups, so the DPS is pretty solid and fast.
Most mobs turn like blue in Katta missions once you reach level 80, if you need alot of aa's it maybe worth staying at level 79 until you reach your aa target.