Say you have a pretty standard party:
BBN 1 w/Power Attack and Cleave, wielding a 2H sword, at 14 Str and 14 Con, does 2d6+3 when not raging, which should autokill a standard Orc, and with Cleave, should be killing two per round. Raging, can't be killed with one blow unless the Orcs get a crit.
Round the party out with ROG 1, SOR 1, and CLE 1.
Say the Rogue and Sorcerer have Point Blank Shot and Precise Shot, Rogue with shortbow, Sorcerer with light crossbow. The two of them together do 1d6+1d8, so 8 points on average, easily killing an Orc (without using magic). The cleric probably doesn't have the feats to have a reasonable chance of shooting into Melee, so hangs back and waits to heal the meat shield.
This fight almost certainly uses up a heal from the Cleric, and some crossbow bolts. Might well add up to 25% of the party's resources for the day. But ultimately, the party should gut two Orcs like fish in a stand-up fight.
This party could probably even take on four to six, especially given a round of ranged combat, and that the Barbarian can charge farther than the Orcs can (so long as he can avoid getting flanked). In that scenario, arcane casting becomes more important, and the Cleric's crossbow comes into play since at least at first, nobody's in melee. If you change the Barbarian to a Fighter, it gets a little trickier since he can't soak quite as much damage and can't rage.
I'll grant you, if the Orcs get an ambush on them, then most of the party probably dies. But then again, two Orcs from ambush is, as stated before, more than an ECL 1.