What are your resistances at? A couple purple elixirs could help with that.
Spell Shield and Aura of Guarding would offer some additional protection.
If you approach slowly, you should be able to draw off all the other creatures, then be able to go in and face the dragon rider alone.
For a warrior, if you drink a shadow potion and use the spin attack near (but not directly on) a creature, you will hit it without turning visible. Flash Attack combined with Stun would help you attack first and more often.
Blind then Hell Spikes is very effective, as is a couple casts of survivor's Curse (it is cumulative, so even at level 1 it can significantly drop an opponent's resistances) and then any elemental attack (or Polymorph).
Scorpion traps are quite overpowered, so should not have much trouble with him.
