I did almost purely instance grinding from 60-68, and could really notice the experience gains through each instance. My team has hit 68 and I've hit a wall in that I've done all instances up to Black Morass and Shadow Labs at least 15 times and I am bored stiff of them all, but the next instances available are all level 70 and I seem to be lacking the dps punch I need to achieve success (Black Morass is owning me atm). Trying to avoid questing because I'm on a PVP server where EVERY ALLY I PASS tries to have a go at me and then calls in fiends, and I hate wasting time corpse running when I could be levelling.