The current default weights for Fire Mages were created with koralon’s burning touch. That legendary item is one of the strongest, but also heavily reduces the value of Crit on your gear.
If you look at the results, you’d actually get higher DPS by reducing crit on your gear in the case the default was created for. If you have different legendary items, you should create a custom gearing strategy based on your gear to use until we fill in the more adaptive gearing strategies.
Here is another post where some people discussed fire mage gearing strategies: