Training Exercise Library

My Loremaster is having extreme difficulty with the training exercise quest for the Dol Amroth library. She can take down the first two corsairs, but the three at the fountain take her down. I have tried not to aggro the third
corsair, so I only have two to deal with but can't seem to accomplish that. Is there another way to the library? I seem to be missing something. I tried kiting but that didn't work either.
Any suggestions would be greatly appreciated.