Sorry to necro this thread, but the Garon's Mutation quest is STILL not completable. Please TRY to fix this, and the other Morrock Wallinder quests that are broken, as this will break this part of the game and drive EVEN MORE of the Player Base away from Runes of Magic, likely cutting EVEN MORE into GameForge/Runewaker's Profit Margin.
Situational Update: It seems that the only way this quest has been fixable is by running the Weekly Server Maintenance, resetting MOST of, if not ALL of the buggy Morrock Wallinder/Kalume Callaway questline quests. Although this ends up being little more than a temporary fix for many of the players who need this questline completed for toon progression, at least it's a step in the right direction. At least it has worked out this way for my toon.