The fights seem fine to me. Honestly the only thing I think needs to be changed is the BA need to be a little easier to hit without compromising their ability to leap-frog across the battlefield efficiently.
I haven't used Machine Guns or Flamers against them yet though, so maybe that will work better compared to the lasers I tried.
An LBX-20 seemed to do the trick but that's kind of a waste (a funny waste).
Machine guns seem to be the only effective way of killing BA's. However you can't always compromise other weapons for MG's on a mech. I think the BA's are a little overpowered at this point to be honest.
MG, RAC Flamer and LBX are really efficient at taking out BA. If you are trying to target them with small/medium lasers, PPC or Gauss you will have difficulty hitting them because you're using the wrong tool for the job.
I also think one of the reasons some players are perceiving BA as overpowered is the utter lack of tactics being employed. Try keeping units together and assigning roles to the members of your group. Having a Harasser or a 'Mech equipped with MG and Flamers will make short work of any BA that attempt to attack your formation.
Just like an M1 Abrams does not use its 120mm cannon to take out infantry, a 'Mech is "doing it wrong" if they are trying to kill BA with large caliber weaponry. The exception is the LBX, but its shotgun-spread nature makes it have a nice area effect.
Lag is also a factor in trying to target BA, try improving your server connection or use a DEDICATED server with a more limited player count (22-24) and it will improve the overall gaming experience.