I'm no Drizzt fan, but a 20th level fighter would probably still win if orcs tried that. Starting the grapple provokes an AoO, the resulting great cleave should clear the decks for the next round. If they hang back, he spring attacks in (more great cleaves) and out again. On the chance that an orc manages to make the melee touch attack to grab the fighter, he's going to have to be very lucky to win the opposed grapple check (fighter +20 + Str, Orc +1+str) to actually start a grapple.
If the orcs are lucky they might roll well early against a weak fighter and prolong their fate, but typically the fighter will be taking down eight orcs per round and the orcs will almost never hit. It will take a while, but I would still put odds on the L20 fighter.