Cresselia is indeed a massive tank. During mini-tours, last round, and this round, I haven't find myself struggling to get past Cresselia, though. I think the biggest misconception I've heard on IRC channel and on the forums is the need to
counter Cresselia. This strikes me as an absurd notion (countering a defensive mon?). From experience, you don't need to counter Cresselia; in contrary, all you need to do is
pack more than one Pokemon that's not walled by Cresselia. The emphasis is now on the opponent switching in Cresselia on your mon rather than you switching into Cresselia. And from my experience there are plenty of mons that can put major dents to Cresselia to make it useless if it ever switches in on them. Here's a quick list:
- Absol
- Aerodactyl (Taunt & Roost)
- Aggron (CB)
- Armaldo
- Bouffalant
- Cacturne
- Crawdaunt
- Crustle
- Durant
- Drapion
- Druddigon (HC & LO)
- Entei (SubCM)
- Escavalier
- Feraligatr
- Fraxure (DD Taunt & Eviolite)
- Gallade (SD & Lum / Sub)
- Golurk (LO)
- Hariyama (Guts + Payback)
- Linoone
- Pinsir
- Rhydon (SD)
- Sawsbuck (SD)
- Scolipede
- Scyther
- Zangoose
- Accelgor (LO)
- Eelektross (Acid Spray)
- Haunter (LO)
- Jynx
- Magneton (Metal Sound)
- Samurott (Taunt or SD)
- Spiritomb
Quite a list for a Pokemon "that walls 95% of the metagame." Then of course there's manual Rain and Sun that adds more to the list of Pokemon that Cresselia fails to wall:
- Floatzel (BU + LO)
- Kabutops
- Kingler
- Omastar
- Gorebyss
- Poliwrath (BD)
- Emboar
- Entei
- Magmortar
- Moltres
- Charizard
Also there are Utility mons that can force Cress out or cripple it
- Clefable (Encore + Status)
- Cryogonal (Haze + Status)
- Lapras (Hydration + Status)
- Mandibuzz (Phaze / Taunt / Status)
- Misdreavus (PerishTrap / Stallbreaker)
- Whimsicott
Now include Hail into the mix, and I found Cresselia an impenetrable wall on paper, but perfectly breakable in practice. From my perspective, RU has more than enough tools to deal with Cresselia. Sure, Cresselia is a major centralization force, as is any other good Pokemon like Sceptile, Entei, Slowking, etc. However, it does not restrict teambuilding to the extent that demands its banishment imo (and as shown through the list of mons that Cress doesn't wall).