I've been hearing that there are some issues with stealthed mobs as I've been leveling up, but until today, I've never had a problem with them. The issue was when trying to target a mob that stealthed and neutral to both factions. I ran all around Dustwallow trying to target (using a macro) these mobs, and all I managed to target were some toads. The mobs in question were the Theramore Infiltrator for http://db.vanillagaming.org/?quest=1201
Has the Nost team recognized the untargetable stealth mobs as an issue, or is there some way to find and kill these things?