Hmmm the usefullness of steal teams seem quite limited bearing in midn that all characters that can use stealth only stealth themselves exept for Teebo. For it to work you need to be able to stealth your healer otherwise it is not all that useful in pvp since your opponent will kill your healers first.
Could be situationally useful in PvE, may have to wait until maybe they release some better synergies for him. On his own he doe snot seem so bad, until you see other characters with all of their ability blocks, offense debuffs etc. which seem better options.