agree with what everyone said.

Better weapon. At least the i70 weapon you can get on the market board. (looks like a flower) if not get the Yagrush and unweather ASAP

let the tank pull agro, get a couple of hits in then regen. devine seal and presence of mind + cure 2 until you get the tank back. Anticipate hits if you can.
If you are about to lose the tank, benediction-> regen -> swiftcast+regen II (I know its an aoe heal, but it casts another regen on the thank. and at this point the tank should have a nice handle on agro)---> shroud of saints and carry on with your cure/cureII.

this is what I do and Never pull agro and have only let one tank die on me ever. (when in DD the tank pulled the entire first floor LOL biggest pull I have ever seen...ever lol)

ps. make sure your not accidentaly in cleric, it can/has happened and absolutely recks your heals.