[Halancar]

Banishing works, but you have to realize that it scales hugely with priest level.

A level 1 priest casting banish will kill, as a rule of thumb, one or two basic undead a round, and you have maybe 10 to 15 rounds untill your meat shield routs, so you would need one priest for every 10 to 15 undead to win that battle.

On the other hand, a level 3 priest should be good for 10+ undead killed by round, so one for every 100 undead should do the trick nicely. Plus, they can switch to smite to deal with any thug that won't let themselves be banished.

And of course, getting higher levels is even better. So whip out communions if you can, equip mage-priests with crystal shields, empower ordinary priests with blood 1, do whatever you need to get those levels up !