There is a max dps cap in the game. For beginners its around 2*e308 / 2*10^308. Even if your crusaders would be capable of dealing more damage, the game blocks you from doing it. This makes you stop somewhere around the mid 1500 areas, with a boss being invincible (it was a real limit way back, thanks to coding and they left it in as a feature after they solved it). But if you complete that challenge then the game will let you go over the limit till 10^400. There are other challenges and a talent in T7 that pushes even further this limit. If you didn't reached that point yet, then it wont do anything for you, but you presolved a future hardship.