A lot of mobs get stuck (intentionally or not) on ledges, leaving them inaccessible to all but ranged attacks. A lot of characters aren't ranged based or have no powerful spells. This leaves us with the only option of standing in ****'ing Ice Storms, get Webline snared and have Greater Dispel Magic spammed at us as we patiently chip away at those sacks of hp with our wet noodles. Things like this make what should be a fun experience, into a frustrating one. Arbitrarily placing mobs on ledges with no way to physically access them is quite ****'ing stupid, as progress is blocked until all mobs are killed. This is resource intensive and depending on how many 'bug' out on ledges to be tediously spammed down.