I’m using Pathfinder 1e for the game stats. We’re assuming four 3rd level fighters with +3 STR and DEX and +2 CON bonuses, which isn’t uncommon using the “4d6 and drop the lowest” stat generation method.
Breastplate gives a +6 to AC. Add +3 DEX bonus and you’re at +9. Add a heavy shield for another +2, and the character’s AC is 21. With an attack bonus of +1 with his shortsword, the goblin needs to roll a 20 to connect. If he’s smart and uses his shortbow, he needs an 18.
Meanwhile our hypothetical 3rd level fighter has STR 16 for a +3 bonus. He also has Weapon Focus (Longsword) for +1 to-hit, and he’s using a Masterwork longsword for a further +1 to-hit. So he’s cranking +8 on his longsword hit rolls. To hit a goblin with AC 16, he needs an 8 or better. It’ll be the same if he has a Masterwork bow with Weapon Focus. With an assumption of a 3rd level character having 3,000 gp, our fighter can easily afford all three items (breastplate is 200gp, a heavy steel shield is 20gp, a Masterwork longsword is 315gp, and a Masterwork longbow is 375gp. Total 910gp).
What’s this all mean? It means the goblin has a 5% chance of scoring a melee hit or a 15% chance of a ranged one. When the fighter strikes back, he’s hitting 65% of the time. If the goblin hits, he’s doing 1d4 per hit. If the fighter hits he’s doing 1d8+3 with his longsword, 1d8 with his longbow. With 6HP, odds are a longsword hit is killing that goblin, and two arrows will probably kill one. With a CON bonus of +2, a 3rd level fighter is going to have around 27 HP (max HP at 1st level, average 7.5 HP per level after), so he can take 10 hits from goblin arrows or shortswords and still remain standing. In melee, that means it’s likely going to take a couple hundred attacks by goblins before he’s in any real danger as he’d dispatching a little over one every other turn.
With an Average Party Level of 3, and four of these fighters (because the CR table assumes four or more PCs), an average encounter should be CR 3. Goblins are worth 135XP each, so a CR3 encounter will involve just shy of six of them. An “Epic” encounter (CR 6) would involve 18 of them. In melee, our four fighters are killing 2 ½ goblins per turn, meaning the average encounter should last three turns or so, while the “epic” one should last seven turns or so. In neither case are the goblins likely to kill even a single member of our party.
That isn’t even a fight. It certainly isn’t heroic by any stretch of the imagination.