First: Use all your Attribute Points on strength.(at level 30 you will have 192 attribute points)
My set: Headwear: Night Vision (Random Enemy - Zone 4) Gloves: Murderer's Wraps (Specialist - Zone 5) Bodywear: Nightstrike Armor (Specialist - Zone 5) Leggings: DarkFiber Leggings (Random Enemy - Zone 4) Footwear: Black-Ops Boots (Random Enemy - Zone 4) Two-Handed Arms: Emerald Death (The Hydra - Zone 4)
Edit 1: The last image of my ability tree haves the wrong stats, I was using the Imperial/Royal set, not the Specialist/Black-Ops set, my mistake, but the ability tree is the same, to see the correct image, please, click here.
Edit 2: If you use Corrosion you can even make a higher damage, 505322 damage.