I have seen them put to good use in Praxix but haven't really tested it so I can't say how good they are there

I have only managed to run them succesfully in Zal discard but with mixed results,...

Basic rules for an OP rant

1st
Find a conditional card and present it absolutely in the best case scenario:
Wow an X/X creature for just Y mana!, that's OP!, Wow this card deals Z damage for...