This keeps becoming a point of contention on my DFB teams and honestly I'm not entirely sure why it's become so widespread. There are only three badges available from the DFB trial: The one for not killing the Vahzilok boss adds, the one for killing all of the Lost boss adds, and the last, Hydra Stomper, is simply for completing the trial.
I know how people are getting confused - Drowning in Blood, the next trial up, has the Brotherly Love badge for killing the giant Shivans within 30 seconds of each other. But people keep stubbornly insisting otherwise for whatever reason. The game doesn't expect level 5 characters to sync kill two beefy AVs like that, relax.