I tried that Forretress and it did wonders!
It was a nice counter to most Gliscor cuz most opponents thought I switched it in just to setup Rocks or Spikes... insteed hitting them with HP Ice for a-shit-lot of damage (most Gliscor users were trying to setup on me with SD but than got 2HKO'ed by HP Ice).
Dragons like Dragonite & Mence were also trying to setup DD on me but got destroyed by HP Ice... same for the Earth Kami Landorus.
All of the listed Mon's are 2HKO'ed,exkeept Dragonite at full HP thx to Multiscale, but its more offensive sets are allways 2HKO'ed after SR Dmg - 252 HP 252 SDef Carefull Nite isnt...it's just 3-4HKO'ed after SR Dmg...
Pain Split did a nice job as well - annoying most stallish Mon's and specialy Chansey & Blissey (unless Bliss has Flamethrower).
In my opinion this set should be listed as an competetive set in the OU metagame to Forrestress.
I'm crazy... I'm insane... Everyday it's ticking in my brain... Just like the rain... Falling down on the floor... Like someone have been shot through a door... Poor poor poor... Little attention-whore... *sing'z*