One of my few 100% IV Mons is a Blastoise with WG/HP. The A-rated attacking moveset. I have him powered up to level 36.5. He is badass!
And he is useless for the most part.
For far less work and candy an ok Vape can do what Blastoise can in a more efficient manner.
I keep my Blastoise maxed out as I think it's one of the coolest looking mons in the game. Sadly he's just outperformed by more common mons.
So no - there is no practical use for him that a more common mon can't do better.