Sniper is beatable, but the fight just feels unfair. He has range and damage. If he is ahead you can't fight him, and if he is losing he can turtle like a monster using towers and high ground.

If the game had a concede option, I'd quit as soon as someone picked Sniper. He remind me of old Tinker which was also a hero who had insane advantage defending the base.

I'd still nerf Storm Spirit first though.