Not sure if they changed how to finish the catalyst. Is it where you have to heal guardians with noble rounds? If so you can finish it pretty quickly. Go to Shuro Chi cp with someone get a few kills to get your noble rounds ready, and have fireteam member walk into ads an take damage then heal them. Rinse and Repeat. If you don't have anyone to help you out, feel free to add me, and I'll help you finish it.