OOC:
Hrafe is not good. He isnt evil either. 2 magi who have already decided to die for the realm dying to stop the avatar of an icon which is commited to the destruction of order.
The math is simple. Even if 2 magi die, we come out ahead.
The Magi dying is their duty. We have the chance to destroy a superweapon in our enemies hands. Sacrifices are necessary.
Also, there is a distinct possibility that Salix and one attack will kill Big Z and the lizardmen dont get to coup de grace multiple magi as it can only target one creature even of it normally targets more. So the risk, is definitely worth taking.
Also theres a huge chance(3d20h1 its a miracle it hasnt happened yet) that disengaging from Big Z results in a crit, which could very likely kill Hrafe.
Many immediate definitive disadvantages to lettong Big z run away. No tangible immdiate benefits to letting him live. Gambling against certain losses for unknown benefit is foolish.