Common cards are now capped at 3 instead of 4.
In other words, “not more than 3 of any individual common” can now be played in a Primordial deck. Increasing the variability on common cards (currently 1.5 times lower than in a classic constructed format) aims to slow down the strongest decks/sets, without disturbing the weakest ones too much… and after several days of testing, it seems to work quite well!