(title might be a little misleading)

Many games that have dedicated, pre-constructed classes have quests just for those classes to give them special advanced gear or core skills and abilities (i'm looking at you, Shaman totem quests). I always found class quests to be a great way to get a feel and RP connection with your character. After completing one, It feels like I've actually attained something of eternal use. In Skyrim, any school of magic found the (only) class quest at the end: once a skill has reached lvl 100. In ESO, I'm not too sure how a class(or rather, skill)-quest would manifest, or what the reward would be, but I hope that there are some unique, playstyle-defining abilities that have to be sought out to be attained.

What do you guys think about quests that reward you with new abilities? Do you like them or do you find them to be a nuisance? Would it cause imbalance in an game like ESO where every skill is optional?