Reese mostly duel wields for crushing damage of 10-15k. He uses his Wirlwind Strikes several times during the fight as well. If that was it, he wouldn't be too hard. But in addition to this, he can double punch for 100-150k, the highest I saw being a double punch for 147k each hit. This punching can happen to anyone in melee range.
Double healer mercs 105+ on reactive, melee with 120k+ hp pulling out when they get punched for heals, and enchanter group runes made him a manageable fight.