The mission mobs in this are Argonaut x2, Longu and Armax. Getting a global per 100 mobs killed would be a real feat, so if you did the mission chains on tehse LA-s, you might expect to get at most 644 from missioneering. So getting to more than challenge 3 completed sounds rather hard.
If you don't want to partake in one or the other, well that's fine but don't critisize someone for setting an event up.
Why not? It is with critisism and comments that allows improvement, when MA makes an event there is always ranting on MA. They learn from ranting.