You said it yourself.
Everyone as a patern and that goes for teleporting too.
When you cast fireball in svs you do not aim at where the sorc is. But you do aim at multiple teleport possibility by looking where they are when you see them on the mini-map. It will not hit often granted. But then again you do not need many hit to kill with fireball sorc and this strat make it so the ice sorc will never have a chance to give a hit. Cause each time the ice sorc get near, the fire sorc is gone again.