Rome Total War- Battle strategies

[M. Demetrius]

I hate javelins throwers because they usually run before they even have time to throw their spears at the enemy

Well, that's what skirmishers do. They also run away and scatter, often leading a cavalry unit on a merry chase waaaay the heck out of the battle. You can't call them back without turning off the "skirmish" mode, but if you do, they usually get slaughtered. After their javelins are gone, you can use them to hold an enemy for a while (if you do turn off that mode) and then hit the unit with something else in flank or rear attack, then withdraw the light infantry. That's often how they're really used, so it is fairly realistic.