You've got the strength build to help with the stamina that most other builds will not have.
I use Fire Axe even without Sex Rex, but yeah I wouldn't use it if I didn't have Miner 69 because it definitely wouldn't do as much damage without that.
Also by your own admission you lose the AOE knockdown, but your also losing out on the guaranteed single target knockdown.
It has AoE to some degree, it often staggers ones near my target but I don't know the % chance. It basically always knocks down single target though, I don't know if it even has a chance not to. Even in the video on the feral military zombie it staggered him on 2/4 hits and he never got an attack off besides the initial one he hit me with, which was mostly just me dealing with OBS stuttering my game while recording
I'm not saying Sledge doesn't have more stagger, just that the Axe has "enough" on it's own. Watch my video if you don't believe me, it staggers or knocks down literally every single zombie it didn't one shot.
Where melee weapon viability kicks in is when you get groups of zombies or face individual tougher zombies like ferals and rads with significant health. Clubs are good at pummeling tough enemies and keeping them a non danger on the ground and get bonus damage on downed enemies. Sledges are good at area knockdown and doing high alpha strike damage and get bonus damage on stunned enemies. Blades are good at hitting multiple zombies quickly and then bailing to let them bleed out and are also very stamina efficient...they also have very high attack speed and can dispatch single zombies fast with chained power attacks. Stun Batons are weak AF but are made to work in tandem with junk turrets. Knuckles are good at repeatedly stunning an enemy.
All of them have a significant chance to explode zombie heads automatically, which can defeat stronger zombies much faster than otherwise possible with a melee weapon. I'd say axes are prolly better than some weapons unperked, but that's where it ends.
That's why I say the Axe is good in all stats, but it's only S tier in block damage. Stamina, Range, Damage, Attacks Per Second, Block Damage, it's basically A tier in all of them. Sledge has S tier damage and F tier speed and stamina, Spear has S tier range and C tier damage etc. The others all have trade offs, but the Axe and Club line are basically "I'm really good at everything but am not the absolute *best* at anything".
I think Axe beats club because Miner 69 is like 400 thousand times more useful than Pummel Pete, especially when the end result is just two very similar weapons. The Axe is a bit slower and takes more stamina than the club I think, but the block damage is much higher so that's why I say they are side grades to each other.
Like if you made a tier list of the weapons, it would look something like (Note, range seems basically broken in A19, you can hit zombies at SUPER long range with basically anything)
Weapon
Damage
DPS
Speed
Range
Stamina
Stun
Spear
C
B
A+
S
B+
D
Club
A
A
A
C+
B+
A
Sledge
S
D
F
B+ / A
F
S
Fire Axe
A
B+
A
A
B+
B+
Knuckles
B
A
S
F
S
A+ / S
Machete
D
C
A+
B
A
C
Stun Baton
F
F
B+
B
A
F? / ???
Junk Sledge
F
B
S
S
SSS
SSS
Disclaimer - (ratings not exact because I don't have the game open with full builds for each weapon type in front of me etc)
You basically end up with the different stuff having different pros and cons, but two stand out as basically being "pretty good" at everything with no major downsides (at least while melee range is buggy). The Club and The Fire Axe are great all around. They have "Enough" in basically every way that you don't *
have* to make concessions.
As for fighting a group with any melee weapon . . .yeah no. I mean you can, depending on what the group is, but if you round the corner into 4 irradiated wights and 5 feral military guys with your knuckles out, they will take them off your hands (with your fingers still in them) and give your sphincter a knuckle rub with them for you. I wouldn't even use a sledge in a situation like that, that's pure 100% "Oh ****!!!" Shotgun time while you hammer that S key for dear life
I mostly consider melee for 1-5~ish zombies depending on how many are running. In groups that size, the Axe, Club, and Sledge all perform quite well. Machete, Stun Baton, and Spear leave much to be desired, and Knuckles require the magazine line + a lot of perks so it's hit or miss and they are late game.
Junk Sledge is . . .really weird in handheld mode, it will throw them all over the place but not kill them, but in placement mode it's a fantastic ally if you have enough points and magazines in it. It attacks so fast it can actually dish out okay damage despite it's ridiculously bad damage per hit, but it ragdolls them away so it doesn't actually get that many hits on them before they get yeeted out of the battlefield. In placement mode with it guarding a door or something, it's SSS tier, in handheld I want to say it's F tier but it's really not, I'd take it over a Machete or Spear or Stun Baton for sure because it will stagger the zombie while you run away