So, coming back to this, I looked up the relevant page in the DMG (page 274) and then looked at what a 1st level character is meant to fight as per XGtE (page 90) and we get.
Level 1 Character, 1:1 with 1/4 CR, with an AC of 13, 36-49 HP, and 4-5 Damage Per Round.
Now, what is 'balance'? Well I believe that is going to be the crux of the discussion, but ahem..
View attachment 145488
Balanced, despite what low ranked players in a competitive game will claim, is 50%, as our good man Thanos, is well aware.
Average roll on a D20? 10.5 or so Google tells me.
Fighter Proficiency at level 1? 2.
Ability Modifier to meet that 50% success rate on attacks? Well now...1.
10 + 2 + 1 = 13.
Balanced, not optimal, not most effective, would therefore be a nice, hearty strength of...12.
Right? Not Optimal! Not even really effective, but if you are looking at a balanced encounter 1 on 1, where 'balance' is a 50/50, thats it.
Heck, the DMG even has the Attack Bonus of 3, which again lines up nicely with our 2 Proficiency + 1 Ability Modifier (due to 12 Str).
I've never even bothered to look at that stuff before, but unless I'm crazy that lines up with my gut expectation that the game is probably 'balanced' around a +2, way more than expecting a +3.
Now I'm off to contemplate the balance of the universe, while I walk my dog.