I just did this fight the other day.
Before you enter the cave use your cleric to cast bless, chant, armours ect...
When you get in cast entangle asap, then with your mage launch off a fireball or two, all the while pumping arrows into anything that is still moving. By then your tanks should be able to finish off the sword spider and other undead. I also found that a well placed lightning bolt is a perfect way to finish off the spider queen
