General advice:
-Never skip the Pyramid. At level 16, even a poorly equipped character can finish it easily. With a two-handed devastation weapon, it should have been a pushover.
-Never pacify the Big Room. It is almost always more work than it is worth.
-Killing cats isn't a mistake. Don't worry about it.
On your specific situation:
-Ice vortices are quite slow. As long as there aren't too many and they aren't too close together, or all congregated around the stairs, you should just be able to outrun them and/or kill them with whirlwind. Make sure you aren't burdened or satiated/bloated. You mention non-autocursing artifacts. Does that mean you have the black torc? 10 extra speed could help here. If you have a wand of webbing (or there's been a spider factory around already), that could help immensely too.
-If you can sneak passed the Big Room, head to the Griffyard and get the elemental gauntlets for cold resist.
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.