Playing as CW there is a lot of bugs associated with set bonuses such as the 25% recovery on your tab skill flat out not working ever. Some of the other sets you have to occasionally re-equip a piece to get the set bonus to start working.
I'm not sure if other classes have similar issues with their set bonuses but it's been a known bug for a long time, just wondering if there's any light at the end of the tunnel here.
Comments
It would be nice if they compiled a list of what actually does and does'nt work
BLOOD neverwinter wiki - http://neverwinteronline.wikia.com/wiki/NeverwinterOnline_Wiki