Depends what kind of damage is your build doing...
You'll probably use it on bosses so conc effect is a good general choice.
If you're elemental, Elemental Damage with Attacks will give you similar dps as conc with greater coverage.
If you're bleed - poison based Melee Physical Damage and Bloodlust might be an option.
You may even go for utility like Maim, Bleed or Inc Duration...