People have explained it better, but crit rolls first. If crit fails, you roll deadly strike. Having a high crit chance = less uses of deadly strike = less useful high lords.
You don’t need bis gear but I don’t like highlords because the amulet slot has a lot more flexibility for other benefits like skills (especially all skills), fcr, resists, etc. If that isn’t a problem to patch over with other gear, use it. But you might find that 125fcr or better resists improves your effective clearspeeds.