If you want to make it easy on yourself, I suggest make a "DPS" account a "Healer" account and a "Tank" Account. You could also throw some DPS onto the other 2 accounts for a 3x dps crew (BGs Arena, etc.) Then all u need is 2x dps, and if they have a tank/healer, switch out your tank/healer for another DPS.

I'd move the warrior to the 3rd account, and roll a new pally too, for tanking. Use your other 70s to boost. Once you have a 70 prot pally, you could run prot pally holy priest and any one of your other DPS toons. If you want, you could also swap the shaman to the priest account, and then you can just respec to resto for your healing duties.

If you can always find a tank/healer, just decide which 3 toons you want to use as a DPS combo (priest lock shaman counds cool to me) On my server, you can NEVER seem to find a tank or healer, which is another reason I'm boxing.