"Oh rammus dived me lv 6 and killed me from 50% hp

You're talking about one of the strongest tanks in the current state of the game going against turrets at their absolute weakest state in the history of the game.

For now, the only solution right now is to try to harass him enough in lane that he can't dive. Sorry that doesn't solve the issue, but you need to work around how the game is right now.