A big problem with Winston is the fact that he sucks vs other tanks I noticed. He's OK against Reinhardt since he can zap him through his shield, and OK against D.VA (unless she's full HP with armor) but in general just does no damage to them. He's USELESS as FUCK against Roadhog who was everywhere last I checked.
And people can never reliably heal him sometimes. Unless you have an Ana, he jumps in and will die too quickly to heal him up. The other healers either don't heal him enough (Zenyatta) or have to get really close to the enemy team to heal him (mercy, lucio)
They can't really buff his damage so he's better against tanks either because then he would destroy squishies. I think a smaller cooldown on his jump would be great.