Everything is viable. I made an impalezon last ladder on d2lod hardcore, funny as hell. You take off 10-15% of normal bosses' hp every hit when you hit.
In d2r i should think it is even more viable since every hit is a guaranteed uninterruptable hit, which i guess works on bosses too.
You deal a lot of damage, but yes, it probably does hit a bit slow.. that is why you focus on the more important monsters while the merc takes care of the lesser ones. You go straight for the big target. It's actually quite fun.