Whoever said there is no imbalance is simply wrong.
So here, in my opinion.
Top 3 heroes:
Twisted fate (Best ganker in the game as well as having excellent lane control. His teleport can even be used as an escape).
Twitch (As far as I understood, the rat is hardly used on the american server. On the EU he is pretty much the best late game carry there is, simply because there is no other hero that can out-dps him in a 5v5 fight. Also, a great ganker. The player with the highest elo on europe is a twitch player, not surprisingly)
Teemo (Map control, nice dps and blind for the opposing twitch/yi.)
Kayle (Her ult on a fed dps really does wonders.)
Blitz (You know those stalemates where the weaker team is hiding in their base while the stronger team feels like they cant push in due to too much AoE? This is where the long arm of Blitz solves the dilemma.)
Rammus (Good initiator with flash. Can lock down a caster in teamfights with his taunt and being generally indestructable. Great chaser for mopping up those who flee.)
Udyr (Yes, the beastyboy. So, he is extremely hard to kill. He can also kill someone if he is allowed to chase him across the map. So what?)
Heimer (So he has 2 nukes. Why not just use veigar or annie instead?)
Katarina (Dont get me wrong, Ive player with some pretty awesome Katas. Its just that she is all about her ult and it can be interupted. She is also fragile.)