Trynda is incredibly strong at late game, but with a team who have trynda it's pretty hard to get to late. He is annoying in mid game fights because his ult, but he is not a beast at that point (unless he is fed, but that is unlikely). Exhaust and cc-s are hard against him but that's not shut him down, his ult keep him alive too much, you need 5-6 sec constant cc to deal with him, and even if you can do it, his mates will slaught you because you wasted all cc on trynd.
So: No, i don't think he is OP, but an annoying champ with stupid design. That's why he must be concidered as a weak pick., unless he got a remake. (i don't think he will in the next half year.)