Yes, but the 600 have a fortress on their side. Plus not all 10,000 can attack in one round. Many has to wait until the people in front of them died to that they could move forward, be killed, and let the guys behind them repeat the scenario.
And let us not forget that these are orcs they are fighting. In all generic fantasy orcs are nothing more than cannon fodder.
Actually, I find it to have that kind of Song of Roland feel to it were the good guys kill a hundred of the bad guys on each of their attacks, but the bad guys only get to kill a couple of the good guys so that they occassionaly look like a threat.
Also, if it looked like the good guys actually stood a chance in Hades of winning all the suspence, build-up, and dramatic elements would have gone to waiste. Sorry, but watching battle scenarios is about as dull as a rubber ball gone flat. Need we be reminded of Inchon, or the endless number of of bad war movies made almost entirely of battle-plans and fight shots?