stop parking your characters in an INN or major city, this will reduce the amount of rested time you get when you are logged off.
I personally think that a dungeon is the fastest way to burn up your rested time.

I hated that first boss too. Last time I beat the first boss i did it by bringing the whole team up to the boss so the concecrate from my pally would help break anyone frozen in ice. I usually drop my fire elementals after the pally has good aggro.