Here's a set that I use and that works great for me.
Move 1: rapid spin
Move 2: scald
Move 3: dragon tail
Move 3: ice beam
Item: Assault vest
Ability: torrent/rain dish
EVs: 252hp/252spdef/4spatk
Nature: sassy
It's extremely bulky on the special side and is a great rapid spinner. Rapid spin is the main reason to use this Blastoise set. Scald is there for an attacking move and with a torrent boost (or rain boost if you decide to use rain dish) it does some kind of damage. Dragon tail is there for shuffling and is another way in which Blastoise can support your team. Ice beam is there for bulky grass types and some more coverage. The EVs are there to make it as specially bulky as possible and it can still take physical hits. The nature improves its special defense even further and I put -speed because I wanted dragon tail to at least do some damage esppecially against latias, latios and goodra.
It is a good answer to aegislash, as your opponent assumes you are physically defensive, and a lot of special attackers.
I really like the idea, i'll try it probably.