It's better than allied MGs, that is for sure.
big arc, good RoF, good suppression and good ability. And it's cheap as hell on top of that.
1vs1 around rank200-150, I see regularly up to 2 HMG34 to support and lock territories. The HMG isn't too good or too bad, it does the job if you support it well.
You cannot take the HMG34 in a vacuum without taking in account all the strength the faction has in the IA department.
The true is USF didn't need the Mortar and OKW didn't need the HMG34 in the first place. The mortar was broken the HMG34 not but it doesn't change the fact those changes are simply game breaking.
finally someone with good sense!!
and yeah, you get flaktruck to defend you flank and put 2 mgs defending mid, there you go, now you have locked 50% of the map.
On maps like crossroads or kholodiny, this is backbreaking since you have no room to manouver as allies.