I'm sure everyone will agree, the most time you waste comes from corpse running. Why are you dying so much? Is the warrior unable to maintain aggro, or is the priest oom?

I was running a similar setup but with a druid/priest combo, controlling the druid as main much as you are using your warrior. I ended up just tanking with the priest in the end because I went for pure dps from both toons (with a shad specced priest, the druid could not hold aggro without losing too much dps), and it just worked out easier this way as everything dropped so quickly. I can say that I never used the dots (too high a mana cost for a target which would die well before the dot had ended) unless it was a boss fight, so it was mainly Mind Blast/Mind Flay for the priest,supplemented with a shield/renew macro set up for casting on either toon.