The answer to this is to have chaotic players at the table playing chaotic characters who don't follow orders or scripts and who are going to do their own thing - whatever it might be, probably different every time - in any combat that arises. And if you ain't got such players, become one yourself.
Again, you seem to be focusing only on the optimal choice. What about the fun-risky-entertaining choice that maybe isn't so optimal?
Put another way, instead of thinking "what does the flowchart tell me to do now?", think "what can I do here that nobody will expect but that also (hopefully) won't lose us this fight?" And then when something comes to you, just do it. Don't ask anyone if it's a good idea, never ask permission - just effing do it and let the chips fall where they may.
Front-liner #1: "Where'd Jocasta go?"
Front-liner #2: "Dunno - she was right behind me a minute ago as my backup."
Front-liner #3: "There she is! She must have found a way to sneak around behind them! She's got their caster down - and crap, she's about to get swarmed....."
In this instance, I'd probably be Jocasta's player.
That's what I'm proposing: thinking outside the flowchart is what keeps the brain engaged; and if an unexpected action doesn't present itself in this combat, it will some other time.