I thought it was over the top. I get that all the aliens that went into the self-imposed quarantine would likely die, but for all of them to die PLUS the ones that were still on their world at about the same time doesn't make sense, simply because it didn't take varyin' metabolic rate into account. Sure, they would all die, but it wasn't like there was a tickin' clock for all of 'em.
I did, however, like the little girl's answer to Delenn's question. It reminded me of my oldest nephew.