I havent paid much attention to the changes to these details, but I have to agree about the AC10 overheating you mention.
Not only do they overheat after, in my opinion, far too few shots, but once they do overheat, they take an overly long time to cool down again.
The AC10 are pretty much the primary weapon of the Warhammer B, making it the worst possible choice, again in my opinion, to take out.
The few times I have taken it out, I cant even take out a light mech as the few shots I do get off are not enough to kill it, and by the time the guns are ready to fire again it only takes 1-2 shots before I'm dead.
If you ask me, taking any mech which has the U/AC10 as primary weapon is a death sentence, as the remaining weapons are not enough by far to keep up with the output of most other mechs.
As for the LBX guns, I too feel their damage output is on the low side.
The LBX is based on the concept of the shotgun.
"In MWLL, the Lubalin Ballistics-X AutoCannon, or LBX, is essentially a Mech-sized shotgun." thats a quote from the MWLL wiki.
I never played CBT, so cant say anything about that, but I remember the LBX from MW 3 and 4 and they did more damage there than want I feel they do here.
I wanted to check the damage compared to other ballistic weapons in MWLL, unfortunately there dont seem to be any available fro the LBX cannons yet, but then again I dont think the wiki site are complete yet so some things are bound to be missing.
My impression is that you need at least 2 LBX 10 or 20 to be able to do any reasonable damage.
Taking the Bushwacker with the LBX20 dont quite seem to cut it damage wise.
When in the Puma B I cant seem to determine if its the PPC or the LBX10 that does the most damage, though it feels to me like its the PPC even though I would have thought it should be the LBX10.