For a Frost to Frost swap, Focus Magic is superior if it pushes you closer to/lets you reach 33.34% Crit. It easily beats RoP if this condition is met, because of the interaction Crit has with Icy Propulsion. It’s been tested/confirmed by the mage theorycrafters several times.
It’s also not an entirely passive talent in a true sense because it requires both of you to execute your DPS rotation properly, and it rightfully comes with an additional risk/reward of providing better DPS if you both live through the fight but falling off if one of you dies and the other person has to change their Focus Magic target to a less than ideal target.
Just to shed some light on what prompted my initial query, my sims are (rightfully) giving me totally different results because if I do a Focus Magic swap and use the Sire Denathrius Crit trinket, it’s actually weaker than my other options. However if I opt into Rune it is stronger than my other options. If the optimizer is running based on sims, it should be able to factor in a 5% crit buff on yourself to do its job.
Thank you for listening and opting to add it in as an option for the optimizer. I really appreciate it.