*Hemlock appears in a puff of smoke, in response to @ mention*
If @
Hemlock is right, though, then other PC builds get to those damage levels anyway - so if you nerf the -5/+10 you don't preserve the relevance of the MM, you just reduce the relevance of fighters. (And after typing this but before posting, I've got to your post 716. The task of lowering "par" is interesting, but I don't have
anywhere near the grasp of the system to contribute meaningfully to that discussion. But happy to follow along and chime in if others are taking the issue up.)
Currently there are three ways I can think of to get massive at-will or virtually at-will damage in 5E. (Caveat: I don't consider DPR to be the most important statistic, but it is what you guys are talking about so here we go.) Roughly in order of most to least effective:
1.) Minions can make you do 2x to 100x as much damage as a normal PC. Necromancer skeletons, druids with a bag of rats and Animal Shapes to turn them all into rhinos, druids that Planar Bind a ton of hags and have them all form covens and spam dozens of Lightning Bolts per turn, etc. Can easily do hundreds of points of damage per turn against AC 20 by level 20.
2.) Quickened Agonizing Repelling Eldritch Blast plus appropriate spells can make you do around 1.5x to 3x as much damage as a normal PC. By level 20, can easily do 100+ points of damage per turn against AC 20 if an external ally grants advantage somehow.
3.) GWM or Sharpshooter plus appropriate spells and magic items can make you do around 1.5x to 2x as much damage as a normal PC. By level 20, can easily do 75ish points of damage per turn against AC 20 if a Crossbow Expert Fighter with advantage.
Oh, and of course there's also (4) the "massive magic item" route which I tend to forget about--a 20th level Fighter using a +3 Flametongue longsword and Dueling style (d8+3+2d6 fire+STR+2) can do 85ish damage against AC 20 when he has advantage, and still have his bonus action left over, e.g. for a GWM extra attack (106 damage). I tend to forget about magic items.
In contrast, a 20th level Thief with a nonmagical crossbow would be doing around 41 points of damage under the same conditions (advantage, vs. AC 20), a Dueling style 20th level Fighter would also be doing 40ish points of damage per round, a regular non-tricked-out Warlock just doing Hex + Agonizing Blast would be doing 50 points, a Dragon Sorcerer would be doing 25 points, a non-GWM 20th level Berserker would be doing around 45 points when Frenzying and 30 points when he's not, and a Paladin would do about 30 points with a greatsword or 29 with Dueling style and a longsword.
So if you eliminate minions, eliminate at-will cantrips, and eliminate Sharpshooter and GWM, and don't hand out any powerful magic items, you probably
would get pretty close to having all PCs do approximately the same damage (30-45 DPR), except of course for spellcasters who would now be on the bottom rung unless expending spell slots.