Since I have very rarely (in the last 25ish years I have been running maybe twice) seen 2 player both as the same class building for damage at a table. So I don’t get this at all.
as I said uo thread if we were playing in my current game and removed the fighter I have (psi warrior play test) and slotted in either a sword and board fighter or your variant human duel cross bow weirder. The sword and board would be MORE help... we have a warlock /sorcer who alreadyis ranged and a rogue... the sword and board fighter would be better equipped to grant the rogue sneak attack (at 5th level that is 3d6 extra damage)
Sharpshooter is the true culprit here. A damage bonus combined with two abilities that can negate penalties to hit. Not even GWM does that.
And that's being applied to Ranged, which is somewhat better than Melee already.
Small correction made above.
I would say this particular combo does alot of damage. However, I would say that other combinations relying on allies casting buffs like bless also enable the same combo even without precision attack. That to me says the high damage really stems from sharpshooter as most all those other buffs and combinations are mostly fine without it. That said, all this is assuming you consider that the fighter being the damage king is an issue in the first place. It's arguable that he needs the higher damage to really be balanced with other classes. So I personally I'm not trying to make the claim it needs removed - just that we need to understand just how much damage this is actually doing - especially compared to classes that don't use feats for damage.
5e is very forgiving. You don't need optimal builds to perform well. But when you have an optimized build in with a bunch of non-optimized builds it's very noticeable.
(I don't consider GWM overpowered btw)
For fun I looked at a level 9 Barbarian Zealot Barbarian using reckless attack. GWM is pretty similar to a comparable barbarian without GWM if that Barbarian has a +2d6 Greatsword/Greataxe.
Doing a quick and dirty computation I actually got about 5 points more on average not 7, but since I don't know your assumptions that could be the difference. Still 5 and 7 isn't all that different.
BUT
still don't think it's overpowered. Sharpshooter can be done, literally, from a football field (American) away and nothing will beat it at range (its the only feat that does as much as it does) . Whereas GWM can be beaten in DPR by polearm master (by how much depends on how often the extra AoO attack comes into play, but it's always significant) so it's not the ONLY DPR feat for any given build - and the additional effects for GWM are ribbons while the ones for sharpshooter are extremely useful.
I don’t think y’all are getting this.
at level 4:
it requires a +2d6 weapon for a sword and shield fighter with the duelist style, also using precision attack and having 18 dex/str to do comparable damage to the fighter with 1 hand crossbow with 16 dex, archery style, SS, XBE using precision attack
this stays the same all the way up through at least level 11 (I didn’t check beyond that).
*note this includes both PCs raising their primary stat as appropriate on the remaining levels.
Minor Quibble - GWM additional effects are strong. The are enough to add about +20% damage on their own.
20% seems like a lot.
Assuming your bonus action is free, you get about 5% extra on crits since you get an extra attack (unless you have a crit fishing Str build) and then some for downing enemies (I suppose this is roughly calculable but 15% seems high). How did you get 20%?