I think a common theme I've found for the challenges is the hardest part being the bugs in the encounters. Perhaps I'm more prone to seeing them for some reason, but the Balance challenge was definitely the least buggy since it just involved NPC's being inside the terrain but otherwise still acting normally and targetable. Resto one suffers from the friendly NPC's occasionally doing some rather dumb stuff in P1, the eyes exploding for almost 400mil damage even in the first room, the NPCs in the damage gauntlet spawning adds regardless of them being healed to full in time and disappearing, the dumb LoS issues during the wave healing section, and Jarod refusing to tank the boss in the final phase. Guardian ones I've already vented about a long while ago. Does the Feral one suffer from any annoying bugs before I give it a good try?