Nothing stated in the patch notes (3.0.1.2) or in the main issues log, so reposting again.
Per Destiny 2 Update 2.8.0:
Obtaining the MIDA Catalyst is no longer impeded by playing with Clanmates. Drop rates were adjusted and now properly scale with the Clan "Catalyst Seeker" Perk bonus.
Added drop chance for wins at Glory Rank 3 Fabled (5% without Clan bonus, 10% with Clan bonus)
Increased drop chance for wins at Glory Rank 4 Mythic (5% > 10% without Clan bonus, 10% > 30% with Clan bonus)
Now guaranteed drop for any win at Glory Rank 5 Legend.
Have won matches at 5500 and no catalyst.
Please let players know that this is bugged. Competitive PvP is certainly not the best place to enjoy the game.
Thank you!