@Man_iLoveFishing That video is fair and illustrates your experience. It seems you are suffering from desync a lot which may also be the reason you have issues with hearing the tgm earlier (?). It looks like the first example with the sound also had some desync issue. If you stop the video on the frames around 00:02.11 (in video clock) you see it going to your left.
I have never experienced anything like that and even from that glacier I have heard tgms coming way earlier than in the video whether it is in heli, in a ground vehicle or simply on foot. I also see plenty of pilots react to my own tgms the moment I shoot them from the side or behind so they are also hearing the tgm much earlier than in the video. However it seems we have different experiences when it comes to how early the sound is heard so there's no point continuing that discussion. Maybe a bug report should be made regarding all the desync.
But in the end this have nothing to do with the current nerf on the tgm. As I previously said the tgm pre buff was fine and there were no reason to start messing with it. tgm after the last patch is more like a glorified recoilless so far. Of course I need to use them more to adapt but my opinion is still that the last nerf was going overboard just like the previous buff was overboard the other way.