My group played with this scenario for the first time this last weekend. And it was awful.
Normally, we play at about difficulty 8-9, and we tend to do very well: we usually don't flip the Blight card, and when we do, it's usually very late in the game. Since Rituals of the Destroying Flame is a 3, I picked a difficulty 5 adversary (one of the Jagged Earth ones; I'm a playtester). We got absolutely brutalized. By the end of round 4 there were maybe 3 lands on the entire board that weren't blighted, and the next Ravage was pretty much guaranteed to end the game by a massive margin.
We tried again, this time with the same adversary dialed down to difficulty 2. We haven't played anything as low as a 5 since the first couple of months we played the game. And it was still really, really tough. We won, but the blight card again flipped in round 4 or so, and there were only about 6 Blight left on the card (in a 4-player game).
We tried different kinds of spirits; in our first game we focused on spirits that didn't really mind Blight, and in our second game we focused on spirits that got a lot of energy and were more about controlling than destroying. Both were bad. Is there a trick to this scenario that we just didn't grok? Or is it really much harder than a 3?