The heavies would all be more balanced if they were tied to teching like it is, but right now with call in meta the KT deserves to be the best because it costs a fuckload compared to the call in tanks.
But it IS the best. It's not as good as it was, but you can't deny it's still absolutely the best heavy tank in the game. I'd gladly give up the IS-2s speed for the KT's main gun. Destroying an AT gun in a single shot with it isn't unusual. Actually hitting something (well, infantry) with the IS-2 is.