Bile Bomb is infinitely more useful against Res Towers, and much better at sniping them, not to mention that Bile Bomb doesn't cost personal resources. You're also assuming that you can get all 9 Babblers to constantly attack the extractor, and tha…
I see no problem with it. Making it a 2-Hive ability means there is only a small window of time anyway before Grenade Launchers and Flamethrowers become available, and at that point Babblers would decline in usefulness dramatically.