I haven't had a ton of time to play, so my 5x hunter team is only level 29, with about 2.5 days /played. I probably spent at least 1 or 1.5 days of that time just getting to 15 so I could start dungeons, as well as getting professions leveled up (4x engineers to get goblin jumper cables, everyone with 1st aid, tailor, enchanter, leatherworker)

Currently my team is working through Gnomeregon - I'd like to get everyone a hydrocane, the loot in general is pretty useful, the dungeon itself is fun and reasonably easy to manage pulls, it's both close enough to resupply points to not be annoying and it has a vendor and mailbox in the dungeon so I can mail myself a bunch of ammo and not have to leave the dungeon until I'm ready.

My strategy in general hasn't been to be fast, but to enjoy the ride. I've been entering dungeons before I was really ready - 2-3 levels before you should enter them - and while that has lead to a looooot of deaths, it's more fun for me because I enjoy the sense of progress when I both figure out how to survive fights where the odds are against me, but also it's great when my team dings (and then again when my pets ding) and suddenly things that were impossible become almost possible and eventually routine.