When I had just hit 85 I made sure to get a tabbard (s) for the first faction I wanted to raise. Picked those that had good revered rewards for class that I was closest to hitting.

I found Halls of origination the easiest.
Grim botol has lots of trash for rep, but found the named a bit tougher there.

In halls of origination I used CC when first starting, partly for practice partly cuz I would die if I didn't .
Remember to have purge/spell steal setup for the flamelord fellow (in a couple of the trash mobs) once he engages and starts chain casting fireball (the buff drops his cast time to .5 secs I think). In the first room he is found he will cast aoe fire at first , which I always ignored as I pulled out of room. But eventually he enters the fray and does the fireball thing.

Good luck!