stop trying to counter Cresselia with offensive mons, there's your problem right there - very few can wear her down before she beats them and even fewer like getting paralysed. Nasty Plot Slowking dances all over Cresselia,
252 +2 SpAtk Life Orb Slowking (+SpAtk) Surf vs 252 HP/116 +1 SpDef Cresselia (+SpDef) : 36.71% - 43.24%
Hardly walking all over Cress, and if it carries Toxic (admittedly unlikley) Cress can quite possibly stall out King
252 +6 SpAtk Life Orb Slowking (+SpAtk) Surf vs 252 HP/116 +3 SpDef Cresselia (+SpDef) : 44.14% - 52.03% In the worst case scenario
252 +6 SpAtk Life Orb Slowking (+SpAtk) Surf vs 252 HP/116 +4 SpDef Cresselia (+SpDef) : 36.71% - 43.24% A more likely scenario given Cress outspeeds
and a simple Toxic Slowking hard walls any Cress that lacks Sub or a Toxic of its own. Ferroseed gets risk-free Spikes on any version that doesn't use Calm Mind or HP Fire , a decently bulky Pokemon like Munchlax (crap), Mandibuzz (poor) or Steelix using Toxic + phazing move (Steelix can rarely fit Toxic) can deal with her in all situations sans last Poke Sub Cres. A decently sturdy Pokemon using Substitute and without a weakness to her coverage moves can use her as set up bait - Jynx, for example, cannot have her Subs broken by any Cress that lacks a SE Hidden Power and even then it can just use Lovely Kiss.
Not entirely accurate. Gallade for example will lose to Cress even if it carries Substitute, and it has 115 base SpDef!
Murkrow can just Perish trap her for the gg, there is loads of stuff really but you are going to struggle if you're using a bunch of fast, frail set up mons and if you keep giving her free switch-ins because she has been thriving against that sort of team for years now.
Not sure what to say except that Murkow carries little viability against the majority of RU.
and stop thinking that hitting her super-effectively is some sort of holy grail, she isn't THAT inconvenienced by Dark or Ghost types on account of their weak STABs - Escavalier on the other hand...there's a full stop right there unless she's using HP Fire which has sone pretty unimpressive damage output against escavalier depending on her SpA investment (even at max SpA and +1 Escavalier survives the hit 2/3 of the time)
It has been mentioned before that Cresselia beats even her supposed offensive counters, and that she 2HKOs Escavalier with HP Fire, meaning catching it on the switch once or hazards accrual equals a dead Escavalier.