I mean the other's characters movement that you observe. I think I know why it feels so bad and unpredictable. One of the reasons is it's too fast - especially the strafing speed but that's not everything. The thing is character's legs aren't changing their position and angle with the side movement. An excellent example to follow would be counter-strike 1.6 where player torso angle follows the player aiming while the legs move at the angle the player is strafing.
https://youtu.be/k2tTgPPtxc0?t=34 Like here from 0:35-0:40 you can see how the head and body are looking where player aims but the legs and feet are moving with his strafing. If there's a possibility you can make the player models in Sandstorm to have such movement pattern it will be a blast. That way your brain could predict where to follow with your aim and not just spray and pray for the best.