Personally I find bats very manageable to deal with but I recognise that they are a pain for those who are ill prepare so my suggestion is instead of directly nerfing bat stats and behaviours how about you change the spawning conditions. If you have it that light from fires reduces bats spawn rate within the area of the fire lets say 5-8 blocks. This would mean while you are online as long as the fires are kept lit you are safer from the bats and can do you daily tasks and whatnots at a small cost of wood but vice versa if you go off the next day you will have to start it again if you are alone or if you are part of a group or village you might have people on that can keep tabs on it. This also adds the idea that if the fire goes out because someone neglected the fire that it could be considered more the persons fault for letting the bats spawn rather than the devs being unfair and having it out for you.
Now, I really don't know much bats or the spawning of animals and as far as I know something like this could already exist, if this is the case ignore this post but if this is an idea that could be added to the game please feel free to add to this discussion.