In theory, sure. The way the game plays, that's not the case at all. I've not once used pass on Heather to aquire treasure, there's no point.
I would say any unit that is "good" is too reliable overall. As in, they don't have a clear weakness for the other side to exploit well enough for it to show. (as in, any low RES unit has a "weakness" but is irelevent due to shit enemy mage stats)