Psyker
3.5-5% Strength for 3.5s on Hit. Stacks 5 times.
Continuously chaining more than 2 attacks gives 2-5% Power. Stacks 10 times.
-8.5--5.5% Charge Time on Chained Secondary Attack. Stacks 3 times.
Gain between 3.5-5% and 14-20% Critical Chance based on current level of peril.
Tac Axe for everything. Headtaker and Decimator work great with Tac Axe's high attack speed to quickly build up stacks during high density moments. While Brutal Momentum is great, with Warp Splitting and Decimator working together to increase cleave, it's not required. Decimator also helps even the odds against tougher opponents, push attack heavy into light spam builds up stacks on tough opponents quickly.
Electrokinetic primary for Reaper/Shooter/Gunner suppression. Secondary for controlling Elite groups, opening Bulwarks for Zealots/Ogryns and zapping Flamers/Trappers/Bombers quickly.
Assail for hordes, sniping Destiny targets, Snipers, and dumping into a horde at the end of Scrier's Gaze during Warp Unbound, preferably when Precognition is at 30 stacks from Tac Axe so Assail gets benefits from Warp Rider, Warp Splitting, Malefic Momentum, and Precognition all at once.
Disrupt Destiny for movement speed and Finesse buffs.
Note: This build takes time to build up momentum through all the various buffs mentioned, but once it gets going it's a pretty strong build. Probably not as "meta" as some other builds, but very fun.