Funny thing, I once did one of these on a fire tanker and forgot that I had taken the damage aura at 1 instead of the shield. The cadavers got to about 1/2 health before I noticed, but we still got the badge.
As for the suggestion, I don't think it needs to be changed. Yes, you can fail getting the badge, but you can always run another DFB and try again. Also, the badge is just a badge, it doesn't contribute to an accolade power, so there is no harm in not having it.
Finally, anyone who kicks someone for failing to get the badge is just a jackass. I've never seen anyone kicked mid-DFB, but I believe you that it happens.