The more I fiddle around with Stakataka, the more I think that Beast Boost really isn't a good ability for it. I think it's the only case where you must purposely gimp its stats to make Beast Boost work the way you want it to. Which is not to sell it short, mind you: a Rock/Steel with a poor man's Moxie and self-made Trick Rooms is pretty damn threatening. But having to take away from the bulk it is very clearly supposed to use just to make it serviceable is kinda sad.
The main problem I'm seeing with Staka is that TR Sweeper is the only thing it's really good at. 20 years and Game Freak still hasn't realized that a tank with no recovery isn't a tank; Rock/Steel just isn't a generous defensive typing no matter how you slice it, and it plainly needs items that aren't Leftovers in order to function (Z-Crystals, Assault Vest, Air Balloon). Be it a Wall or a Trapper, there are simply other bulky Pokemon with less caustic typings that do the job better. With TR Sweeper as its only niche and Gyro Ball and Stone Edge almost guaranteed to be in its moveset, the only mindgames you can get out of it are whether your third move is Earthquake or Superpower, making Staka incredibly one-note.
Personally I'm wondering if having Skill Swap with Staka in Doubles is the right way to diversify it, though my first thoughts of it didn't quite work out: I was thinking of having a Doubles partner with Moxie set up either the Trick Room or the Skill Swap, but it turns out Trickers or Swappers with Moxie don't actually exist.