Actually, I feel like I didn't put nearly enough thought into this, so let's take it up a notch. Okay, so right now, they have +2 plate, +3 shield, +3 longsword. That's pretty vanilla. Let's add a cloak of displacement. Now they will suffer 16 HP damage, total, in approximately 1/6th of the fights, or an average of 2.67 damage (actually slightly higher if we add in the vanishingly small chance of more than one orog hitting double natural 20s, but eh). Oh, and that +3 longsword is now blackrazor, so the fighter can haste themselves and gain 46 temp HP every round. At this point, they can just stand in the middle of the room and kill infinite orogs. That might get boring, so at some point they swap the longsword for the flail of Tiamat to take out wave of the orogs at once.
I've barely scratched the surface. Suffice to say that once we allow significant magic into the equation, this fight is probably not worth playing - just tell the fighter they kill the orogs, it takes about 30 seconds, and move on.