Ok, I'm on the third story mission on the Wei campaign, and for the life of me I can't beat it. I'm level 11, and this's pissing me off actually. The three Zhang brothers are in one circular room, and there are these Yellow Thunder things that apparently give Zhang Jiao strength. The objective is to kill him, but those three keep ganging up on me and hitting me so much that I can't even get up. One time I did kill Zhang Jiao once... and what happened? He came back to life twice as strong! Is there something I'm missing, or is this mission even possible?