These are the ~most significant things in each patch:
Launch: Oct 6, 2020
Patch 2: Oct 27, 2020 (3 weeks after Patch 1=Launch)
-- Bug fixes & cinematic tweaks, "75% of you stood with Tieflings...Good outweighs evil." Nothing significant in this patch.
Patch 3: Dec 2, 2020 (5 weeks after Patch 2, 8 weeks since launch)
-- Experience for pacifism, adjusted companion behavior to make them "less mean", party auto-jump, 2 short rests instead of 1, rebalanced cantrips to no longer create surfaces.
Patch 4: Feb 25, 2020 (12 weeks after Patch 3, 20 weeks since launch)
--Druid Class, loaded dice, targetable portraits, and various dialogue, story, & combat changes that add up to be significant