Yeah, as a user of Sonia, this would piss me off. Sonia's active skill involves changing the board to a random distribution of red and black orbs. Sonia has a secondary skill called Row Enhance, that says when you make a row six across of a single color, you gain bonus damage for that color. Because of the Row Enhance, the best possible outcome for her active is to get 18 of one color and 12 of another color, allowing you to make a stack five high of alternating colors:
xxxxxx oooooo xxxxxx oooooo xxxxxx
Like so. This allows you to maximize the damage from both colors. What happens in this picture however, is that you can only get a single black row enhance, which makes the damage way less than it would be if you had even gotten one more red orb. One more red orb would at least allow a single red Row Enhance and two black Row Enhances, more than doubling the total damage you would do.
Yeah, Ronia is a great pull, but once in a while she definitely throws that trollface at you.
My very first time doing Hera-Ur, I made it to the last stage without much trouble and popped Ronia active only to get 3 red orbs. Thankfully, my ragestone was salvaged by getting one for the clear afterward...
Draco Summoning Circle-Fire & Dark
Red Sonia's Active Skill. Turns the entire board into Fire and Dark orbs.