i always bring thief for dailies, except gold and fairy dailies because she dont boost them. Then again, i have full AW team.
you might want to bring her on gold rush, where every boost help.

ah, missed the 5
she is enchanter, her skill will stop golem for few seconds, and change attack attribute of unit on her range into magic damage.
example, if you put bashira on her range, and use her skill, Bashira will shot magic arrow that ignore def.
she is pretty useful against golem, though raising her isnt a priority.