I never had an issues with teemo.
not even when I was silver.
I can deal even with heimer when I play Diana or talon.
I think teemo is mostly "op" against lower elo players that heavily lack patience.
and that want to fight over everything, instead of giving up when they can't fight and fight when they got their opportunities.
Then again as a low level Diana player that can't rqr, it was easy to me to: don't fight unless the circumstances are favorable for you. As in I can't go in without hitting q first or without being feed.
same thing vs teeto. You don't go in at lv 1-2 lel.
you wait till your power spike and then come up with a plan to kill.