Artifacts, at least in the case of RoI, gave us unique abilities we couldn't have dreamed of doing otherwise. I'd like to see similar stuff in D2, with collectable Artifacts (no power level, like ghosts, only there for the unique abilities). They'd be spread few and far between, but they'd each be unique and powerful. I imagine they'd be cool as strike specific loot. Imagine a strike boss that wielded a massive sword, and the artifact he dropped doing the same as Memory of Radegast, but providing additional lunge range with swords as well? Another could be one from the Nokris strike. To fit with his role as a Necromancer, the artifact could reduce time to revive teammates. Things like that. It would be awesome.