I started two-boxing Hunters a few days ago.

Both at level 70, one fully epic geared and the second in mostly greens.

Won 5/10 2v2 arena games.
Cleared Mana-tombs trash and second boss.
Killed lots of trash in Zul Gurub.

The hardest part is turning follow on and off at right times. Otherwise it turns into 1 hunter with 2 pets.