What settings are you rendering with? Cant get such a sharp picture on my movies for some reason, and the size is even bigger then yours.

Anyway to the encounter i suggest you pull him to this spot, aka concentraion will hit everyone. This is were i tank him: http://www.wegame.com/watch/Utgarde_Keep_Multiboxed/ I heal trought the frost tombs, but that aint realy a good idea with one healer.

Apart from the tips you already got i would like to add:

1. Your priest aint healing, or atleast using heals with a cast time. Are you clicking your chars to do a /assist main/Tank /cast heal? (bind a key to certain chars and use flash heals or greater heals) I also added hand of protection from my paladin whenever my healer needs healing. Its rarley needed,but thoose times when my healer reeeeealy needs meele protection its gold.
2. This encounter screams for prayer of mending, It will make this alot easier if you use it. Trow a renew on your tank aswell.
3. This is a short fight and i doubt mana will be a issue, switch to blessing of kings on your slaves atleast untill you get better control.
4. You lose aggro straight away, bind taunt and taunt the prince back when you lose aggro.
5. Always start with Avengers shield, its awsome aggro and ranged. A great way is to trow avengers shield on trash then sheep them, when it breaks it will go straight for your tank instead of the mages.
6. Always keep concentration up on this encounter.
7. Auras are great tools to migate damage, im not sure if the frost tomb damage can be migated. Try frost resistance aura and if it doesnt work use concentration/devotion aura atleast.
8. Try to use "tab" instead of clicking the target, clicking takes attention away from your health bars and the overall picture. (Im not planning to start a clicker debate its just what i feel works best)
9. Only use divine shield if your paladin is left alone and can kill the target.(or to remove stacking debuffs, then you have to click it off thought and taunt the mob back) Divine shield drops all aggro from the paladin and gets your slaves instant zerged. Use divine protection as it reduce all damage with 50% on your paladin!
10. Use seal of vengance(called something differet for the alliance) for tanking (the one that gives a holy debuff to the target)
11. Tomb damage is frost damage, aka use frost ward on your mages.

About your gear,specs etc:

Dont gem your paladin with spellpower, and dont be cheap with the enchants on your tank. It will cost you more in wipes!!
Your Protadins talent tree is weird: Get touched by the light,combat expertice and deflection atleast. Either use 5 points in Blessing of kings or none. Drop imp blessing of might,seal of command and divine guardian.(get vindication instead, its good vs trash mobs.)
I noticed now that your priest is shadow so respeccing him to holy or disc is the first step. Im not a priest expert but maybe something like http://www.worldofwarcraft.com/info/...00000000000000

Once again gem your gear, green gems costs nothing!! There are loads of cheap enchants to get aswell so leveling enchanting would be a good idea!
Do you use Blizzard on your mages since your specced imp blizzard? If not drop it and use it somewere else!
Im not a mage expert either but i would try http://www.worldofwarcraft.com/info/...33230152201351 instead for pure pve!