Noticed that Sikhism is now a heresy of both Sunniism and Hinduism now. I guess this is preferable to the original situation, where one would only deal with them rebelling when playing as a Sunni nation. I do have to mention the amusing oddity, though, of having Sikh heretics rebel while playing as Punjab.
I suppose a religion DLC would be good to see, however, given that religious groups have unchanged completely since EU3, and Europa Universalis is by far lacking behind Crusader Kings and Victoria in the religion department. We do, in addition to Sikhism, lack Ibadiism (Oman), and Miaphysitism (Ethiopia.) Heretic rebellions additionally have no detail to them, and thus have no proper "succeeding" goal (no converting provinces, no changing state religion.) Buddhism still stands as a single group, Japan stands as being entirely Shintoist (with no special mechanics for Buddhists, instead the biggest religious group the Shogunate seems to fear is Catholics.) The "Pagan" religious group seems to be the least detailed, The Aztecs, Mutapa, and Ryuku all having the exact same religion, having good relations, and getting relationship bonuses with these nations each would never dream existed, the religions not being based upon region.