If we're fighting the Lich King in this, better make this a Raid level difficulty scenario.
To be fair, I think that the rifts are content you can complete with however many people are around, this does include a full 40 man raid. It more. So while it is possible to do with fewer, canonically it may be just as hard as before.That said, canonically the Heroes of Azeroth that we play have already beaten this guy, and likely have greater gear and skill now, given the greater threats we faced since then. Such as, unpopular but true, his master, The Jailer. So I don't really mind Arthas being easier to beat.
Is it just me or is this an obvious asmongold being undead easter egg