What hurts teh most of about the teams with warlocks is that damn shadowfury stun. Everytime I'm about to kill someone, boom aoe stun.

For frost mage, I hope you have frost resist totem on at least one of your shaman. It makes a hell of a difference. Mages are very easy to pressure too, a couple lightning bolts and CL's and they are likely to bubble at that point. The mirror images can be taken care of with a single chain lightning.

For LoS teams, I try to position myself in a place where they can't LoS effectively.
In nagrand, this is going to be on an opposite pillar, but just in front. They will lose range by a few yards if they stand behind the opposite pillar. All they can really do is ice lance over and over.

In blade's edge, near the front of the bridge prevents Los entirely unless they never want to open. put your totems way behind you and they won't be ice lanced.

In dalaran, our best bet so far has been to stand in a corner with my healer behind a box. This requires them to either jump down (where LoS is only possible by running around a corner), or fight on top, where if they get out of range, you're out of their range as well. We find that a lot of teams will go behind the box and try to gank my paladin - at which point they are now in my full line of sight as well as completely out of their healers' line of sight.

ring of valor and ruins are large enough for the same blades edge/nagrand type strategies - they Can los but will accomplish little more than an ice lance, mass dispell, or one off spell. If they come any closer you can start nuking, or at least purge the hell out of them.

Don't feel too bad about your record though, we went 6-20 last night, being paired about against the same 2400MMR about 11 times, and the rest were 1900+. Out of 20 losses, only two were blatant mistakes of ours, the rest were just teams with too much coordination, CC, and most of all - massive dps.

You might swap in a priest or resto druid if you keep getting the same teams, for better aoe healing. My pally and I seem to do better against cleave teams, 2x melee + mage/warlock, or whatever. Other heavy aoe teams seem to need more aoe healing.

Hopefully this is legit, but take this with a grain of salt - our best rating has been 1690 so far on reckoning, but all we get are 2200+ mmr teams, then <1000 rated teams that we farm for an hour then they get lucky and steal 25 points from us and we're back to where we started. Maybe someone with a higher rating can give you better advice