I’ve got 19 total (16 unique). According to the app, I’ve opened 298 booster packs with stamina. Looking at the opening rates, I think there’s ~3.84% chance of pulling a ☆☆+ in a pack - I should only have 11/12 cards, so I’m doing better than expected, but I got some from wonder picks.
Having a distinctive full art Blaine or two would be really useful for me - there were a couple of times I just quickly played a “scientist in white coat” card and accidentally played Professor’s Research or vice versa.