Healer gear optimization is a much different problem than DPS optimization.
The TLDR version is that the set of gear we recommend is one of the many good sets of gear you can use to successfully heal in raids.
If your goal is to get high parses on WCL, that is a totally different goal. When you get to the point where keeping the raid alive isn’t all that hard and you want to get higher HPS numbers on logs… you really have to start finding a way to keep as much of the healing “pie” for yourself as possible.
The popular way to gear isn’t necessarily going to be the “best” way - it has become largely a social choice. “Best” is highly subjective for healing. We added the customization tools to BiB so that people can tweak the optimizer to go for traits and stats they prefer, regardless of our calculations. I’d suggest that you make use of that if you prefer gearing the way you see the majority of players in logs gearing. I can help if you need info on how to make that work.
The gear we pick is based on our highly detailed healing simulations. Those simulations assume a progression-type encounter where you barely have the gear to keep everyone alive. Once you surpass that level, you can start doing a lot of different things that could help you parse better which might not work as well in progression.
I am experimenting with some things for our shadowlands version of the healing simulator and optimizer to calculate sets of gear for a wider variety of encounter types. The gear we recommend, as I mentioned, will definitely work very well for the main role of a healer: keeping everyone alive. But, I know a lot of people are more interested in seeing high HPS numbers in logs. It would be nice to also be able to provide some more options for people looking to make that their main goal.