They originally had two shots as well, but dealt more blunt damage. They are less destructive to constructions now, and have more damage loaded into the AoE DoT burning than direct impacts.

The big problem created by the first balance patch was that while they removed the second shot, they didn't adjust gjall's aiming AI, causing the creature to miss vast majority of its attacks due to trying to saturate an area instead of actually aiming with care. There was also noticeable delay in their action patterns and general idleness.

I wouldn't mind if they dropped something else than just bile bag, but I can't think what it should be. Blood clots? There should be no shortage of them any longer. Maybe just making the base version have 1-2 bile bags could work, but they are easy to avoid and not a common enemy so you can just leave them be unless they very rarely encroach on settlements under your protection.