Just noticed startingWeight is now 1.0 and diminishing returns is 0.2. So looks like it has been changed. Thank god.
So their 3-player GS if they each had 100 would be 240.
Depends on which build the server is on ofc. startingWeight used to be 1.7 and diminishingReturns was 0.22. On those numbers their GS would be 460.
Yeah 300% EXP is not a good setting. You level fast which feels great, but your GS rises 300% faster as well so the enemies are much stronger. Unfortunately your firepower will not be 300% stronger, because firepower is very dependant on things outside of your level and perks (e.g what you managed to loot by day 10, how much ammo you have etc). Your survivability and base strength is also not 300% more for similar reasons.
Just for the record....
Player gamestage = (your level + days alive) x difficulty setting
Since you said the guy who was level 53 has GS 100, I'm guessing the difficulty setting was Warrior: (53 + 10) x 1.7 = 107. The days alive is an odd one. It is calculated as the server's current day, minus 2 for each death. So if your top player had died twice we'd have: (53 + 6) x 1.7 = 100
In multiplayer, your scaled up GS is calculated by sorting the GS for the top 5 players in your group, then using the startingWeight (call this sW) and diminishingReturns (dR) as follows:
GS1 x sW +
GS2 x (sW - dR) +
GS3 x (sW - 2dR) +
GS4 x (sW - 3dR) +
GS5 x (sW - 4dR)
Of course what we don't really know is how a horde of gamestage X compares to a horde of gamestage 2X. Is it twice as strong? Twice as hard? It's impossible to quantify in any real terms, except to say it alters the type of zombies spawned in the horde. Higher GS numbers give more of the difficult zombies.
At the end of the day, Loot 25% and EXP 300% is a lethal combination.