When you deal with grapplers for me zoning isn't a major issue. I tend to pay more attention to the opponent looking for tells rather then worrying about the general picture. Besides most grapplers like to get as close as possible anyways.
The expecption's being Vice's Decide (hcf.K) or Daimon's Jiraishin (dp.P)
Actually Goro's Jiraishin is one main reason I focus on him. If you see the down motion of the dp soon enough it can give you enough time to jump at him taking him by suprise (though online is a pain to do it). Vice's Decide you're right I have to treat her differently cause it comes out too quick to do much. She's a case by case basis depending on how the player uses her.
I will say though looking for tells isn't always about watching your opponent. A classic one is dealing with fireball users. I'll use king as an example. When you listen to her say venom strike it can tell you a lot. If the fireballs come out slow more then likely they are baiting you to come at them. If they come out fast but have a rhythm to them then chances are the opponent is very dangerous in between fireballs. However if the fireballs come out fast and have no rhythm or pattern then more then likely your opponent is throwing them out wrecklessly and is easy prey for a counterattack.
An example on how to use this info would be you hear the slow venom strikes so you know your opponent wants you to be aggressive. So you throw fireballs back to get him to speed up throwing his fireballs. If. You can feel a rhythm then be careful a feint might be a way to work around him, but if you can get him to speed up fireballs with no rhythm then you can roll, or jump attack away cause he's easy prey.