Actually colliding or not colliding Chapel with your opening terminal is probably more important than opening Chapel/$5 or Chapel/$4. And they collide quite a lot of time, while Chapel/$5 isn't very frequent. Therefore, I don't think Chapel being $2 instead of $3 or $4 makes things too luck-based.
Isn't the issue that if Chapel costs $3 and you get a $2/$5 split, you are stuck with $2/Chapel? The difference between Chapel/$4 and $2/Chapel is bigger than the difference between Chapel/$4 and Chapel/$5, especially if there aren't any other $2s on the board. So because Chapel is not the kind of card you want lots of, the $2 price is actually perfectly reasonable despite its power, just like "If this is the first time you've played this card this game, each other player gains 5 curses" would also be properly priced at $2