Q: How does it use Fierce Eye?
A: Assuming we have our epic and it isn't set to never be used, we dynamically check our dot_crit and our spell_crit_chance to determine if we should stagger our fierce eye usage to get maximum "uptime". If for some reason we're just not using our epic or we don't have it, we just use it and don't bother trying to min/max it.
Q: But sic, I want to use FE *BEFORE* the epic?
A: That might be a change we do sometime in the future, but due to how we're currently checking / pairing it isn't the way we're doing it.