EDIT: I found someone in the game that told me a similar thing happened to their Shaman because the patcher wouldn't finish the update. I'm going to try re-installing.
EDIT #2: I re-installed the game and the Z button still does not trigger the effect of Tactic Combo. I'm going to not use my Twin character until this is resolved because I don't want to get used to not using something that everyone says is very useful.
Edited by xbumbrello, 06 January 2013 - 09:28 PM.