The Subway people say such weird things... not to mention Hiker Tapioca. Anyway, I tried running a Sandstorm team with Ttar, Excadrill, and Regirock, and I was up against so many more Machamps, Swamperts, (insert Poke good against Sandstorm team here), etc. than I'd ever seen with a more "balanced" team. Maybe old news, but the Subway builds its teams against you just like the Tower!
I enjoyed defensive Battle Tower teams last gen, I don't see why they wouldn't do ok now.
did you try switching out regirock for reuniclus?