I think asking rec questions within a single game (possibly series) is fine, but cross-game recs can get tricky. Try to use information from the game you are asking about. Comparing to other games is fine, as long as that other game is not the bulk of the content.
In the case of this specific question, I think it would be infinitely better if you described what playstyle you like in DotA and said "In LoL, I liked Kennan" as supplementary information. Having that as the sole fact is bad.
I guess the best way I could sum up my feelings is:
Don't rely on Game A to ask a question about Game B.
Note: I originally voted to close, but I'll admit I was jumping the gun. I am not suggesting closing questions that don't fit this admittedly vague standard. I am simply stating why it doesn't make a good question.