How much overhead are we talking about here? Because if you're just using multiple AV software installed on one machine, 1) holy shit, the performance penalty, 2) you'd still be impacted by this, as CS would have taken it down.
I'd assumed that any essential company would be similar. OK if your purchasing systems for your hospital are down for a couple of days it's a pain. If you can't get x-rays it's a catastrophe.
If half your x-ray machines are down and half are up, then it's a pain, but you can prioritise.
But lots of companies like a single supplier. Ho hum.
Bonus, in case you do catch a malware, chances are higher that one of the three products you use will flag it.
So you have multiple AV products and you target those groups. You have those groups isolated on their own networks, right? With all the overhead that comes with strict firewall rules and transmission policies between various services on each one. With redundant services on each network... you've doubled or tripled your network device costs solely to isolate for anti virus software. So if only one thing finds the zero day network based virus, it won't propagate to the other networks that haven't been patched against this zero day thing.
How far down the rabbit hole do we want to go? If you assume many companies are doing this kind of thing, or even a double digit percentage of companies, I have bad news for you.