This is what i suggest you do Mosg.

Grind your team to 1500 and decide what works and what doesn't in the process. If you can't make 1500 then i suggest either rolling a different team you feel would work, or if you are having fun just keep playing them until you get bored.

The one thing i notice is your poor choice in targets to start with. It is hard to determine which is the healer sometimes but if it's a pally healer you NEED to make sure it uses it's bubble. The best thing you've done is go after warlocks first. (at least that's what it looked like) Anything that can fear your toons needs to die up front as you don't want to be wasting bubble on that.

You've gotten better at healing but you definitely need an "oshit" button like Bubble + full heal on someone or multiple people. I don't know if you have this but it could help. Also since you are on your death knight i cannot tell if you are cyceling divine sacrifice or not. Also make sure that you have your shield up that makes you take more healing at all times. I'm not sure you are at the point where you can just rush in and do enough damage fast enough to kill anything that is pre-hotted for example but then again i could be wrong. I saw you kill the warrior first once, which i was confused about.... it got no healing and you won that match so i guess you can't complain.

Also when going after death knights. Make them use their anti magic shell (self one) and then SWITCH targets to a healer (if there is one) as soon as the AMS is off then kill the DK.

It just seems like it's an experience problem along with some kinks that need to be worked out. I would suggest looking over some tips on how to play a single ret paladin over at arenajunkies.com and applying whatever knowledge you feel is applicable to multi-boxing them in arena.