Is this Blastoise worth powering up?

it resists steal wing, ICE Beam counter dragonite, dragonite resists water gun.

I would not power it up, but it can kill steal wing dragonite under 2500CP（with dodge）

Currently there is no reason to power up any Blastoise to be honest. Maybe only if you can't access Eevees at all and because of that not have any Vaporeons. It's a good keeper though for later, you never know what will change in the future.