I’ve played this season with the black blade of chaos and pushed to 650ish corruption (with a build version with net+smoke bomb, wich is very easier to manage with mana), then I gived a try to the unique 2H Mace Event Horizon.
At 10 stacks, its very powerfull (2 to 3x more than B. Blade of chaos). It’s unplayable in monolith due to lack of movement and attack speed, but if you go to a glass cannon build, you can one shot every boss. Biggest hits can reach more than 1.8M damage. (The weapon is playable in monolith if you reset the weapon stacks every combo).
I run here Decoy for a 82% crit multiplier bonus with the Shift synergie.
Yeah, it’s hard to build around with the increased move and attack speed that comes with the stacks that give you the extra dmg. I tried it with my stun build FG I was working on but just couldn’t get past moving, and especially attacking, so slow. And my egg slam was for attack speed even, albeit at a whopping T3.
I made a 2h melee Blademaster build during the CT for Rogue 'cause they mocked me about it. I cleared the hardest boss at the time (the Dragon Emperor, there were no empowered monos back then).