is your warrior prot? arms? fury?
is your priest shadow? holy? discipline?

how are you dying? who dies first?
your priest does damage too? then they should die quick anyway.

ARE YOU CLICK CASTING??

ok... your cast sequence kinda... sucks? holy fire is great to open a battle. if youre holy, just smite. if you're shadow, mindblast mindflayx2 mindblast mindflayx2 and on and on. reapply pain when necessary.
and your warrior needs to do more than just... charge and heroic strike. =/