That guide is pretty good. I like to set the terrain up for victory beforehand. Put Oil and/or poison barrels in a convenient place, send one PC forward on their own to trigger the enemies and then leg it back to your ambush point. When the enemies pass the barrels, fire arrow and whoosh. Just make sure you're standing well back. It's how I did for Evelyn. If you can get past Deitmar before Evelyn then you're probably levelled enough.
Dmnqwk's points are all well made, especially #1.
