I don't think you understand what made Dehaka viable before, then. What made him so good is specifically that he can waveclear so fast. Synergy between that and his global and his team fight presence means that you get map/exp control (the key to winning most games, not team fighting per se), without sacrificing team fight. And it was balanced, because he's a high skill hero/difficult to use properly, and because he is optimal when paired with another front line since his solo tanking is suspect (viable, but not ideal). His plummeting winrate is directly correlated to the double nerf on his waveclear (primal aggression) and in teamfights (baseline nerf). Arguing about his single target damage literally makes no sense since you aren't addressing his core hero design at all. His lack of speed and initiate with that build makes increased AA damage inconsequential at any appreciable level of play and it shows in the talents win rates.

This is from Nj3Fate and he summed it up pretty well I think.