Use shodokan's grinding method. First 2 mins of stormstout brewery, you kill 40 mobs for about 200k xp, takes about 2 mins, run out, reset. Gets very decent xp. Yes it is a grind.

I 5 boxxed All of Jade Forest and got the achv, then only did half of valley, none of karasang wilds, all of kun-lai and half of Townlong steppes and I was 90.

10 people in IoC i the 85-89 bracket is no problem AT ALL. I would say a full 1/3 of each team is made up of bots (seperate question, has anyone else noticed there are way better botting programs out there now? The bots actually travel round in packs and spam abilities, you can actually die to them).

Are you Ally, if so, IoC is docks, glaives, boss, win, xp, repeat.