FALLOUT's combat (and FALLOUT in general, anyway) was meant to be an as accurate as possible representation of the way PnP Combat is handled. Just as in PnP Combat the DM has to do rolls for every "enemy" after the players take their turn, the same happens in FALLOUT. Slow process or not, it too contributed to the game's great atmosphere.
And, every time you criticize FALLOUT's graphics, God kills a decent RPG Designer. Please, think of the RPGs.