This is my mini-reasearch)
It is from stats of games in ESH FTP div 1 and ESL season 7 QL TDM 4x4. I took one game on each map and calculate how many frags was on each weapon. Maps are: Deep Inside, Intervention, Capmgrounds, Dreadful Place, Purgatory, Realm of steel Rats, Grim Dungeons.Then i calculate the same for 7 maps and that is result:

Frags per game on each weapon on a map is some kind of weapon balance + maplist balance. Many maps have 2sg and 2 rl. So 12 rl and 13 sg on 7 maps. I think that each map have 8 mg's & pummels also because there are 8 players on it.

Before update of 2 February.

Guntlet: 0.2%, ~0.5 frags per game
MG: 2.5%, 5.1 frags per game
SG: 26.7%, 53.5 frags per game
GL: 1.5%, ~3.0 frags per game
RL: 18.1%, 36.2 frags per game
LG: 23.4%, 46.8 frags per game
RG:20.6%, 41.3 frags per game
PG: 9.3%, 18.6 frags per game

After update of 2 February.

Frags per game on each weapon on a map.
Guntlet: 0.3%, 0.7 frags per game
MG: 1.9%, 4.0 frags per game
SG: 11.2%, 23.5 frags per game
GL: 1.6%, 3.3 frags per game
RL: 21.8%, 45.5 frags per game
LG: 28.6%, 59.7 frags per game
RG:22.6%, 47.3 frags per game
PG: 11.9%, 24.8 frags per game

It was a good update!... but MG is still more powerfull then GL.

1) It is nesessary to decrease MG damage again to 3 or replace MG to some kind of Pistol or Blaster from Q2) in 4x4.
No! mg is fine)
2) It is nesessary to do somthing with GL, increase splash radius X2 for example, because now it is weapon only 4 fun =.) or useless =(
3) I think MG damage in tdm 2x2 must be 5. Because players can run 150/150 all the time there. Maybe it is not so important there.
4) Good map for tdm 4x4 is a map with 2sg, 2pg, 1rl, 1rg, 1lg (~ 50 frags per map each), no gl=/. Where you will made defferent frags in weapons.