Right now I'm at level 23 leveling and I'm using the following build after respeccing so many times for free:

5/5 Aimed Shot (Might change to 5/5 NOX, just for leveling)
4/5 Shadow Viel (No Combustion)
4/5 Shadow Piercer (No armor debuff, might change this)
5/5 Combat Medic (THIS IS A MUST, I saved so much money on pots from this)

Rest in general standard passives that suit you.

I rotate the following pets: Mali, Talon, Horton, & Ribbit. Might add in another in the future.

Main tactic is to pull with AS, drop SV, pop Ribbit Arcane, SP around and finish off stragglers with dps spamming. This is after you dropped Medic Packs behind you.

I'm thinking of just switching out AS for NOX just for leveling, mainly for the AoE damage that it does and comboed with ribbit they go down FAST.