That's exactly how it was. The expert power field is the key :)

That makes sense, but how much mana did you spend? And approximately how many hit points does a Death Knight deal with 10 Titans in a direct attack? About 5 each?

I also used the field. Rangers move faster than Death Knights. I would close in, cast spells, bless, close in again, cast spells... and so on. Because the power field lasts for 2 or 3 rounds. I cast all the spells I could on them, especially the Fire Shield, which deals damage in return. Then I stood in a corner and started the battle. I also had to spend mana on resurrection to avoid losing any Rangers.