I think Blastoise is underwhelming as a Shell Smash sweeper and would generally be outclassed by Cloyster and even Omastar in the current OU environment. That being said, if you wish to use it there is some interesting tech that could make it more viable. Earthquake really serves no purpose on this set as Heatran is already easily dispatched by a boosted Hydro Pump and as a coverage move on an uninvested stat it's still pathetically weak even after a boost. It also forces you to run a Rash nature which isn't ideal. Blastoise would really prefer to run Modest. I have seen some tech with Terrain Pulse alongside a terrain setter to provide a pseudo-Weather Ball for Blastoise. You'd likely want to run Lele or Koko for this to give you Toxapex coverage, and you'd wanna give them a Terrain Extender. All in all though I don't really think it's worth it. Have you considered running Blastoise in a lower tier with a more hospitable environment?
I have to echo Tsk's sentiments. Blastoise is going to have a bad time. There's just nothing it offers that something else doesn't already do much better. As far as I'm aware, it's not even that viable in NU, its actual tier.
Edit: Upon further research, it does weirdly have a niche in RU though. Personally though, I think the Spinner/Pivot version is better.
Personally, I like to use a bulky variant myself: Modest Nature EVs: 184 HP / 252 SpA / 72 Spe.
In regards to your set I would change the rash to a mild nature - a water types weaknesses are grass and electric and % wise most of the time the grass/electric moves used against them are special. Rash is a nature that hinders Special Defense which would put more of the disadvantage against the mon in those circumstances. The below is an alternative to your set.
Blastoise has literally one one thing other bulky waters do not have: Rapid Spin. This was a bigger deal prior to gen 6. Blastoise would be OK as a defensive rapid spinner, but the issue is that it doesn't have much in the way of offenses or defenses. I wish that it had regenerator or something.