Just a few quick points, we are aware that HMG are fairly dominant in the current meta game, partly as a result of their durability. It is something we are hoping to resolve in the future.
Keep in mind though, a simple health decrease will only resolve that issue so long as the original crew retains the weapon. Once you recrew it with another squad, the weapon team will take on the new durability values of the crewing entities.
edit: perhaps a received damage modifier would be a better suggestion
i've said it before and i'll say it again... i don't see how increasing the weapon team crews to squad size was a good idea in the first place. even if an MG gets flanked, the unit still has decent fighting power and lots of survivability. in coh1 a successful flank on an MG meant that the MG either had to retreat, or risk giving up the weapon to the enemy. in coh2 a successful flank means that you still have to micro around the MG for at least 30-40 seconds before you have done enough damage so he might think about retreating his MG. in coh1, leaving an MG unsupported basically meant you had 1 less unit on the field (since it was useless) and in a worst case scenario meant that the enemy might capture the MG. in coh2, fighting just with MGs is not only viable, it is even encouraged to some extent with the way buildings work (as in units in buildings just won't die), since an MG in a centralised building is pretty much unkillable without indirect fire units or flamers (and flamers in my experience are extremely unreliable in flushing units out of buildings). this reminds me a lot of a problem coh1 used to have, where an MG42 in a house was pretty much unflankable (because of being able to switch targets pretty much instantly).
the problem with MGs is not the damage they take or the health they have (and as you pointed out, captured weapon teams would regain the old durability... just think of vet 3 KCHs capturing a MG42... talk about MGs flanking you ;-)), but it is much more fundamental. MGs in coh2 are not a support weapon, but a front line fighting unit (a maxim rolling into the firing arc of an MG42, setting up, and outright killing the MG42 crew is NOT a support unit).
i'm not entirely sure where exactly everything went wrong, but if i was a developer, i would ask myself a few questions:
what is the purpose of the unit in question?
what do the players think the purpose of the unit in question is (or what do they use it for) and what do they think it should be?
does getting the unit feel rewarding to the player? ("i'm not getting the croc/brummbär because i think it's a good unit, but because i'm so far ahead that i actually CAN without falling behind. AKA adding insult to injury.")
is the counterplay for the unit "fun"? (countersniping in 2.602 anyone?)
those are just a few question i could think of off of the top of my head.
if you ask those question in regard to HMG teams, you will see a huge disparity as for the intended purpose and the in-game usage (which, imho, can be related to the weapon teams being squad sized).