It kind of depends. You talking standard orcs? Thirty standard orcs would not butcher a high level fighter unless he was built extremely poor and used poor tactics. A high level fighter's AC will be in the 18-20 range. He'll have well over a 100 hit points. He'll be able to dish 22 points of damage or more a hit against orcs using Great Weapon Mastery. That is usually enough to kill an orc a hit. He should be able to take them down at three to four a round eliminating attacks as she does so. It won't be as easy as a caster, but he' can do it.
Back of envelope: on an open field with 8 orcs attacking/round (wolf pack tactics cycling cheese) AC 20 Fighter would get hit by 30% of orc attacks (15+) for avg ca 10 dmg, so 3 hp/orc/round, 3x8=24 dmg, he'd last around 5 rounds, killing around 18-20 orcs first. A big change from pre-3e where he'd typically kill a couple hundred orcs.
If he were holding a choke point he'd be ok, though.
It looks as if a Fighter-20 can be Horatio on the bridge at Rome, but not Ares at Troy, or Arthur at
Badon Hill, unless maybe he had +3 plate & +3 shield - then the orcs would be hitting on a '20' only.