I think they are great now. Or well, they are atleast useful, to your own team now. As others said, if I was on a team where someone bought them I'd shout at them and explain why thats a bad idea. Now when someone says 'I got priests', I say 'Nice, lets push some towers with em'.
I'd say they are working pretty well now. Don't know if its how they are intended to work, but its tons better than buying currency 1, 2, and 3 for the enemy team.
EDIT:
Make that its better tahn buying Currency AND Experience, 1, 2 and 3.