Yes most are buffs, yet not every buff is as valuable.
The accuracy chance is not a buff. Its long rang acc got slightly better yet its mid and close range acc got nerfed. The curve got flattened.
Combined with veterancy accuracy buffs it is a major buff. A vet 3 M20 has around 50% more far DPS after the patch than before (if I remember correctly) only slightly less close (which in most case will not use).
The unit is mean to be used far range any way since it can self spot and does not want to move to faust range.
Build time is still longer then before.
Bazooka removed wich you can buy now from weapon racks yes, reducing the effectines of the armoured skirt price buff.
Imo its still worse off overall despite it being cheaper, getting some vet bonusses in acc. Hence imo it isent used much currently
The timing is difficult to tell because of the many changes to USF.
Think it safe to say that it was not: "nerfed quite a bit over the years".
On the contrary it got more utility. Has a new roles to detect cloaked units and counter sniper and a much cheaper investment to get (both in MP and MU) for laying mines.