Violet Hold has some nice benefits of being so close to an inn, everything is in one room, it's level 75, so should be good to grind from 75-80.

Downside is the first two bosses are random so it takes a little bit of practice to get the hang of all of them.

I haven't kept track of xp/hour there yet, as I still make mistakes and wipe sometimes there. I actually get an upgrade or two, and the gear I don't need will DE into a large dream shard.