I don't believe he is overly stong, it can be pretty easy to stomp a Fizz who has no idea they are doing.
Having said that, I do believe can be unfun to play into, troll poll can negate most heavy hitting spells with the press of a button, there should be more reward to using it and timing it well rather then just press a button and avoid a large chunk of damage.
With the hit that you suggested to his R, that would kill his lane phase, he relies on hitting high range sharks (Which can be hard enough on mobile targets.) and it would be extremely hard to do that if it could stop at minions.
For counters, I generally have a lot of success with
and
, these are all for the same reasons, they have great anti-engage tools in the case of Galio and Malzahar and can out poke him early on, In the Case of Kassadin, he can Teleport out of the way of Fizz's ultimate and then just turn on him, his passive and Q are also very useful to countering his burst.
If you have any other questions I can try to help.