I think i battled this team more than anybody here. I'll do my best to answer!
That Murkrow completely destroys Physical attackers with FeatherDance. I have to say, that Murkrow is perfect.
At first, that Regigigas caused me some problems. But then, i put Golurk and noticed that he completely walls him. I got an amazing set to use:
Regigigas @ Leftovers
Trait: Slow Start
EVs: 252 HP/ 176 Def/ 80 SDef
Impish Nature (+Def,-SAtk)
- Thunder Wave
- Confuse Ray
With a Thunder Wave and a Confuse Ray, the foe has a 37.5% of hitting you. This set is completely walled by Ghosts, like your previous set. After 5 turns, Return will hit extremely hard and it's STAB. Substitute is there for it's usual use.
That Rotom is perfect. I liked him so much that i put him in my team.
That Kadabra is good. I would replace Energy Ball for Substitute and HP Fighting for Signal Beam. HP Fighting is there because it covers more types for 5 less damage. Everything else is good on him.
I am not sure about Wartortle. He.... can work well as a support but still, i suggest Samurott. Here is the moveset i use for him (and yes, i already used that moveset.)
Samurott @ Life Orb
EVs: 252 Atk/ 144 Spe/ 112 Spd
Adamant Nature (+Atk,-SAtk)
- Swords Dance
- Aqua Jet
You can make him your Swords Dance sweeper! Swords Dance and then Waterfall for STAB, Aqua Jet as STAB Priority and Megahorn as coverage against Grass types.
That guy is perfect. With Magnet Pull and Earth Power, trap Steels and kill them so Regigigas can sweep effectively without being resisted. The only problem of the team will be Ghost types but Murkrow can take them out with a STAB Sucker Punch.
Hope i helped you!