Um, Anger and Wonder go into the graveyard and thus Mirri won't be fending anything off. Rofellos will generate tons of mana and Rider will bounce lots of stuff. What deck that uses Mirri can compete with a deck that would typically use Squee?
Probably. But an LD deck with tons of Rains isn't particularly menacing. A combo deck with as many dark rituals as you want is going to be pretty fast...
How would that be of any use at all to a combo deck?
Plus Ritual of the Machine is useless against artifact creatures, black creatures, and creatureless decks.
I have played against a grand total of zero arcane decks. The mechanic does not impress me and apparently it isn't impressing others very much either...