Got a save you can upload from just before or during this?
This might be Mantis material if you can upload a save to DFFD with the problem in progress.
I have an autosave from three days before. I loaded it up and now I can give you his exact stats.
He is legendary axedwarf, fighter, discipline, and observer, master shield user, professional armour user, accomplished wrestler, adept biter and kicker, expert striker, professional dodger, and adequate misc. object user (he also has a few other random weapon skills but those are irrelevant.
It seems I was wrong about the outside patrol route, that must have been in a different fort. They are all cave adapted and experienced nausea on the surface.
This time round "Lord Captain" Mebzuthroder murdered his way through half of the goblins pretty much solo in a fountain of limbs that resembled what would happen if a weapon trap filled with serrated steel disks was capable of locomotion. Afterwards he collapsed from exhaustion. But I noticed two fatalities fairly close to what happened the first time, the first being the militia commander - a hammergoblin got a lucky blow on the commander's hand before the commander even blocked a bolt and he passed out, and his skull was caved in by a scourge. The other one was an axe lord whose shin got crushed as part of a very lazy exchange of blows after he lopped the head off a goblin, and passed out to experience a fate similar to the commander.
I believe I understand what the issue was now. It's simply that cave adaptation is far more debilitating in combat than I had first thought. There were more examples of goblins parrying and dodging dwarf blows than of dwarf blows hitting, and tons of hits which the dwarves were only saved from by their armour, which seems to indicate that it really was just a case of cave adaptation reducing legendary fighters to levels just above those of an ordinary goblin soldier.
Only about a quarter of the melee dwarves were actually outside this time, and most of them are cave adapted, whereas those who sallied forth in the last save were mostly newer dwarves who were not yet cave adapted, which explains the lack of bruises first time around.
Sorry, I believe I've wasted your guys' time, but I think this can at least be taken as another cautionary tale warning you that you'd better organise that your dwarves patrol outside sometimes.