turn Ramza and your main warriors into Lancers and send them to battle (properly skilled on Jump)
you'll probably won't have to count on your luck to hit Wiegraf (step away from him so he has to approach you to hit with his sword skills) and after you defeat him, you can avoid Titan damage by jumping and moving everyone away from the area...
if possible, add Move-HP Restore (from Monk) to your warriors' Move Skill... it will give you a few more turns being alive
bye