.hack//Infection Part 1

Leveling up a few levels above 30 wouldn't hurt. I always found a good third party member is Mistral. You can have her hammer him with spells from afar, and when you or Blackrose get injured, have her handle healing. I also find it helps to shell out a lot of cash to get tons of Antidote, Restorative, and Resurrects beforehand, and split them among your party so everyone can properly heal each other.

As far as battle strategy, just hammer away at him until you can datadrain, do so, then chip away until he's down.