I agree.
Teams like Barcelona and Man City can get away from a central midfielder like Toure who is, perhaps, an indifferent defender because, on the whole, they are much more talented than the teams the are playing against.
I don't think that works in MLS as well in where the whole league is structured to ensure relative parity among the teams.
So, giving Poku meaningful defensive responsibilities is problematic if you don't think he can commit to that type of role. And, even if he can, are you better off giving him more freedom playing further upfield? You actually sometimes see Man City do this later in games where they bring on a more defensive CM and push Toure up as the most attacking of the central midfielders.