I think this may be a bug but I've not seen anyone else report on it. So the guys in my clan noticed that if you had unlocked the outbreak Perfected Catalyst in the zero hour mission (but didn't complete the catalyst), you can now progress the catalyst with just the need for weapon kills and no longer the requirement of the weekly rotation completion of the mission. (Since the drop of beyond light) 2 of the guys in the clan have now completed the catalyst by doing this. I have the catalyst and it was at 4% before beyond light dropped. But now if I go to my outbreak, the catalyst isn't "installed" on to the gun and it won't let me install it either. So I now can't make any progress on the catalyst.... I've tried deleting the gun and pulling it from my collections but still no joy. Anyone else having this problem? Is so... Bungie, please fix this.
Can confirm you don't need it slotted to get catalyst progress. I went from 47% to 50% after running one of the darkness post-campaign missions, just takes a LOT of precision kills with it to get it to budge. Presumably we'll be able to slot it after it completes.
They only way to complete the catalyst was to do the Heroic Version of the mission.