Sorry, but imma need to omnislash this
A Martial will never have 2, much less 3, more attacks though.
Fighter 11, hand crossbows, 3 base attacks + off-hand attack = 4 attacks. Might not look like that much more vs the thief's 1+2x off-hand, but thief scales really bad with haste/bloodlust/speed, whereas fighters hyperdo. And in melee, it is even more stark, as melee off-hand attacks suck, whereas PMM/GWM bonus action attacks do not.
What happened to be Barb and Pally?! You said "it is still not as much as the "martial" having two or three more attacks.", and a Barb and Pally have the same number of attacks; if hasted/bloodlusted/speed they have ONE more, never 2 or 3. To now say you're only comparing against Fighter 11 is like saying "But what about Monk6/Barb4/Druid2?" Martials aren't just one build, Fighter 11 indeed has a lot of attacks and dishes out significant damage, I would *hope* a Rogue with at will invisibility, reliable talent, skills for days, Evasion, and Bonus Action flexibility wouldn't outdamage them! That would make them absolutely and completely worthless, instead of just worthless outside of combat and replaceable inside of it.
GWM, as specified, is a flat +10 damage per attack. That's 2d6 + 1/2/3 (enchantment) + 5/6/8 (strength) + 10, before we add in any of the hilarious extra-damage-per-hit sources; 18-33 damage per bonk. That's nearly the optimal shortsword +3 dex 20 sneak attack damage (1d6+3+5+5d6=14-44) *per attack*. Note that all this is before Supremacy dice, too; the 1d10 evens out the per-hit of the fighter to the ideal hit of the rogue at maximum.
Sure an unoptimized Short Sword attack does nothing compared to GWM, but why would the Rogue in your comparison not be using Sharpshooter? The whole point is, 2d6+3+6+10 before any of the hilarious extra damage per hit sources, is not substantially different from 1d6+3+6+10 before any of the hilarious extra damage per hit sources that Sharpshooter is doing.
Rogues can:
Dash and still get 2 attacks, which combined with their range lets them chase down and eliminate fleeing targets before they pull in more adds.
If we're talking ranged builds, this is not in any way above sharpshooter fighter performance.
If we're talking melee...
That's simply not true though. A Fighter who dashes consumes their action, a ranged build Fighter who dashes gets *one* attack after doing so, not two. A melee Fighter who dashes gets *zero* attacks after doing so, as GWM and PAM bonus actions are both conditional.
Take out priority targets on the other side of difficult chasms or inopportune surfaces.
Fighters do it much better, because strength for jumping, and the ability to actually kill a priority target when it is absolutely crucial, thanks to surge.
If we're talking ranged, sure, again I would hope Fighters specifically would do so as that's literally their entire value to the party. But what happened to Pally and Barb? If we're talking a Melee fighter, the kind who has Strength for jumping, then we get into the situation below.
Disengage while surrounded and still get 2 attacks against whatever was surrounding them
Fighters don't need to disengage; they are likely to kill whatever surrounds them. Or they can
But that's the entire point - I've seen it play out personally multiple times, a Martial character has 3 worthless adds nipping at their feet. They would love to go after the big bad but taking 3 opportunity attacks to do so sucks, and the pathing to get there with them in the way doesn't really work out anyway. So they spend the turn attacking the things that are barely a threat, while if a Rogue is surrounded they can disengage and still fire back on whatever was in that cluster also freeing up space for party members to AOE it if warranted thanks to how turns work, or can spend the 2 attacks on the big bad or whatever else actually warrants it.
Take out multiple disparate targets on opposite sides of the battlefield.
Again, fighters, because jump range is *huge* thanks to strength.
If fighters strength is huge, they're melee, and in that case, no, they can't equal the range of a crossbow's field of fire in a single bound, even with super jump on, and that's not typically on in combat. This is inaccurate.
Meanwhile I'm just chilling dishing out 100+ damage round after round, every round
I'm... gonna need to look at the math behind that 100+ each round every round; you don't get sneak attack with every hit.
Sure thing.
5d6(Sneak)+1d6(Hand Crossbow)+2(Enchant)+6(Dex)+10(Sharpshooter)+1d4(Fire)+1(Ring)+2(Archery)= 28-61 damage from primary attack (average 44)
1d6(Hand Crossbow)+2(Enchant)+6(Dex)+10(Sharpshooter)+1d4(Fire)+1(Ring)+2(Archery)+1d4(Piercing)= 24-35 damage each (2 bonus attacks, average 29, total 58)
Granted, "Every turn" is a bit of a misleading statement, as certainly there are misses, times where it's worth it to turn off sharpshooter, overkill, and times where the damage averages on the low side. But there are also times where I hit the high end (including the 10%+ of the time where I crit, which for me means an extra 20+ damage), and this is ignoring Bless or other buffs, elemental arrows, and so forth. So yeah, average damage, 100+ per round. Obviously this is late game with a lot of magic items at play, but you asked for the math, and this is what my character is doing

while our martials often have to sort out how exactly they're going to get to and try to damage the correct targets, and end up just hitting unimportant targets at their feet instead.
Do they not see the Jump button? Do they not understand how movement works? I don't get it.
We've already covered disengage (which eats their whole turn), but yeah, varied elevation is also very much so a thing, as is hazardous terrain, and suboptimal positions to end your turn. Maybe it's never been a problem for you, but it's certainly a problem for them.
I don't bother disarming most traps, because there are simpler solutions. Tossing crates over them, attacking them, etc. But yes, the rogue has the disarm part on lock better, thanks to reliable+expertise. Perception, though, is not a problem, because barb can easily use items that aren't available to rogues, that boost either perception directly, or give advantage to rolls.
Not really, just saying. I picked up Medium Armor on my Rogue because it granted +1 Dex and gave shields and access to, of course, medium armor. Not just the actual armor itself which is never worth it, but the gloves and so forth as well, in which case Barb has no equipment advantage whatsoever over Rogue. But of course not every Rogue will do that, there just aren't that many other good feats to take a 17 Dex to an 18 while providing another tangential benefit, and it's certainly an option as they have an extra feat compared to Barbs etc.
I had a lot of luck with Karlach scouting around and getting into an opportune engagement position to KO a key target at the start of a fight. I really, really tried hard to find suitable targets for my sharpshooter Astarion, and, eh... Rarely is there a squishy enemy wizard in need of a bolt to the spleen that I can't engage in another way.
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Hey YMMV, if it hasn't worked out for you it hasn't worked out for you. I'm just saying my experience in my campaigns, both Multiplayer where I'm playing as one and Single Player where I've got Asterion filling that role, is that they've been absolutely tops on damage due to the nature of ranged attacks and have contributed massively out of combat as well. If you can't find suitable targets for a ranged character to take out while having no problem with melee positioning that's, well, rather unusual in my opinion but entirely fair, it just hasn't been my experience whatsoever.