I was pulling 2 packs by the time I got to 45ish. I would go from the beginning of the instance to clearing through to the graveyard. The graveyard I was pulling 5-10 mobs. The trick is to LoS/interrupt shadowcasters to clump them up. Blood drinkers hit hard and have a bit of HP which can be hard to deal with undergeared. Witchdoctors have healing totems that you should deal with, but are otherwise easy to deal with. The Shadowhunters have ranged attacks and a hex. I don't recommend pulling more than 1 or 2 Shadowhunters if at all possible. A bad hex might wipe you, a second hex will result in at least one dead character.

Once you get to graveyard, life is quick and simple. I cleared the stair event once or twice. It was more efficient for me to just clear the GY, leave and reset. The gear from the graveyard boss should be the only pieces you really need.

ZF (for me) was actually some of the fastest leveling yet. I found it easier/faster than Cath. I'm just now getting BRD arena clears down quickly. It competes but there's just so much more XP needed at this point.