Since the update, Teebo has a bug. Even though he is invisible, his ability with his primary attack doesnt work in most cases. Also, since the update, my Ewok-Team that should be attacking often, ...
I have been testing it today. It is still a useful ability but not something you can build an entire strategy around, as it used to be. With the old ability, a Teebo lead could pretty much single-handedly take down any single boss by never letting them have a go (but this was balanced by the fact that it is much less use against multiple enemies).