I only started arena a few weeks ago as well and am not particularly good but I bring my priest in and have him spam heal on my shamans dps buttons which kinda works - I found they just got burnt too fast otherwise, so maybe switch one of yours to resto and spam CH until you can find someone to heal for you. There's a couple of threads on here that I found really useful for macros, I'll find them and link them. A few things I've found though:

- focus target priority on your IWIN button helps a lot.
- try and focus a ranged dps (use /focus arena1 macros to quickly focus the same guy on all your toons), keep an eye on where that guy is so when you press IWIN it's used well.
- melee I find a real pain in the ass but drop magma/FN to keep some pressure on their healers and round robin TS while you try and kill a ranged.