The Devs said outright that the campaign ws were "too powerful" to be allowed use outside of campaign. Probably because a lot of them are AoE and do decent damage
I do recall this being said, But outside of maybe the AoE Terror WS the DRK uses, none of them are extravagantly powerful. At 75 yes, at 90 with things like Fell Cleave and Sonic Thrust, they're not as wtfamazing i agree.

Maybe they'll change their minds :X?