I don't build KT's and here are the reasons why:
>too much resources concentrated on a single unit. Lose the unit, lose the complete investment and lose the game
>compared to the input, the output is too small dps & HP wise
>to slow, good players will just play around it or kite it to death
>takes ages to vet and the vet it gets is horrible
I'd say, its a good unit in 3vs3+ games but then again its 3vs3
If you want to buff it, it needs to be limited so 3vs3+ heroes wont cry