Arbites
Continuously chaining more than 2 attacks gives 2-5% Power. Stacks 10 times.
3.5-5% Strength for 3.5s on Hit. Stacks 5 times.
4.5-6% Close Range damage on Repeated Hit. Stacks 5 times.
32.5-40% Damage when shooting Enemies in the back.
New tree looks lit, so here's a build I theorycrafted just looking at the tree. This is a melee brawler that discards the dog in favor of simply not getting hit and juicing your damage, while making sure that the hits you DO take don't hurt that much.
While I can't yet say for certain what to do when playing, you should probably primarily use your melee weapon and whip out your gun for large packs of Dreg Ragers, Maulers, and any specialists you see.