I'm not gonna sit here and say speed drain doesn't work when it does.
However, if you are using a badge slot for ONE CHAMP, that is proof that he is unbalanced. You can deny it all you want but when you have to sacrifice a badge slot for a specific champ, that means there is a problem.
I don't exactly know how many other champs get a speed boost via abilities, but I don't think it is many, honestly off the top of my head I can think of none or at least none that are played to the extent of Khan.
One Khan while beatable, requires teamwork which doesn't happen often due to so many "players" being bots or being worse than the bots, which sadly I have seen.
Two or more Khans? Why bother? Why bother playing that game? Sadly I have seen so many 4 Khan teams and it ticks me off quiet frankly. It ticks me off that Kiz hasn't fixed this terribly imbalanced champ and it ticks me off more than instead of actually EARNING a victory, people would rather cheese and lame their way to win.
I'm gonna sound redundant here but I will repeat it. When you have to sacrifice a badge slot just to counter ONE champion, there is a problem.