I think that Asana could have saved itself and countless thousands of people a lot of pain had they provided a simple option to autogenerate the rules to recreate the old functionality.
So, when My Tasks first gets rolled out, the user signs in and is met with a “Meet your new My Tasks” dialog. But one possible path to follow is a “I’ll look at rules later - get me started with rules that are similar to before” button (… well, perhaps without quite such a verbose label…)
Then, people who don’t understand rules and don’t understand what the changes are, or just those who are in a hurry, could have had a stop gap that keeps them going until they have the time to look at things.
I don’t know if you’re still rolling out the My Tasks to paid customers… this might just save some headaches if so. Otherwise, perhaps this is something to reflect on for the future of how Asana handles very disruptive breaking changes…