The "useless bodysnatcher" is the only one doing anything of value. Jagaaan and Woody obviously aren't going to be able to kill Nomen here and now- they don't even know the extent of his powers yet. But it doesn't matter if he's dead or not, because Ari's stealing the body of an important public figure who'll have easy access to Nomen and Deaderland in the future, once our group actually knows how Nomen can be killed. It's setting up for the future, which is important considering this particular raid is almost definitely going to fail completely.