Benji

Benji is arguably one of the best units in the game. People may disagree with me, but I believe he is S tier. Why?
Benji's passive skill is that he gets 8% power every time he attacks, stacking all the way up to 40% lasting for 2 turns. That alone is NUTTY. To further top off this insane passive skill, his personal is a self heal that scales based on the damage he has done. If that wasn't enough, this heal can be glyphed to cost less mana and cleanse debuffs. Simply making him a Nightblade means he's practically done. He can legitimately solo maps with no investment. 

Ancarant - So, with the Overflowing Karambit of Ferocity, you will attack 4 times in a fight (if you don't crit and kill something). You will only need to attack one more time to max out Benji's 40% power passive. With the Depth Ring, that 40% power passive also translates into a 20% dodge. By self buffing with Fleet Feet, you will almost always be ahead of the speed curve while also applying a stack of Shadowstep, giving you 20 stacking to 40 extra dodge. If you use an unglyphed Moonlight Beacon at 100 mana, you'll benefit from an extra 25 dodge for 4 combats.  At 80 mana, you'll benefit for 8 combats. We could drop the Astral Ring, but I find its super nice to have if we get hit by empowered enemies with higher accuracy or guaranteed to hit empowerments to be able to pop our personal heal - which will most likely heal us for a majority of our HP - if not more. 

Champion - Benji is a decent Champion. He has really good bulk and the 25% additional power scales really well with his insane might growths. Additionally, the 25% power gives you 12.5% to dodge when paired with the Depth Ring. Its quite a bit less dodge than Benji in Ancarant; however, with Nightblade's Shadowstep and Fleet Feet, you could get to a respectable dodge in the Champion class. Benji won't double or quad without significant favoritism in this class. If you don't care about dodge, go Gallant or Seeker. Honorclad, Enchant Weapon and Exposing Light are all pretty decent. 

Reaper - Benji has a decent option in Reaper, given his high Luck (crit chance). Benji can wait one turn, get the Destiny Ring proc and warp to kill something, unlike the others in this class tree that have to wait at least 2 turns. Due to his mastery being low, he can instead fix his accuracy problems by himself with the Solitude Ring. 

Ellisant - Benji is a surprisingly good Ellisant if you can position him correctly to counterattack on enemy phase. By this point you know how good his passive is. Give him a Repeater and use Full Draw every turn. He'll get 3 power every kill on player phase, 2 power on enemy phase. Even if you only kill one thing on player phase and one thing on enemy phase, that's still 5 power a turn and by the end of turn 4 you are on equal footing strength wise with Champion Benji and doing magical damage.