We played through the module with a party of three ~10th level characters, a human paladin, a gnome wizard and an elven rogue/fighter/wizard.
Having no cleric was tough, but we got discount at the church in our hometown after a few visits. "Ok, we need one resurrection, half a dozen restoration spells and some rest. How much?"
Our strategy was: buffing up as much as possible, teleporting in, slaying as much as possible, teleporting out, heal up, rest, repeat.
There have been four PC death's (with resurrection and later true resurrection) total. My own character died twice, once from being swarmed by girallons and reduced (with extremely lucky rolls on the girallons behalf, they needed a 17 or 18 on d20 to hit) from almost 100 hitpoints to below -10 in a single round! The other one was in the final fight from a finger of death.
Well, what can I say. The adventure was horrible! It was very repetitive and no real challenge involved, except fighting armies of undead. Not really exciting, but just very boring in fact. *shrug*
Of course it might also have been the inability of the one who DM'ed us through the spire to run the adventure properly, but I think it was mostly the adventure being just a very dull dungeon crawl.
We made new characters and started a new campaign afterwards (with two new players, so it was not only the adventure's fault - and our characters being 11th~12th level were already fairly powerful and we wanted to change a few rules also)!
My advice: Put it back into the shelf and grab a new one!
Bye
Thanee