Who said that Miko's power are useless?

Very useful for cruelness
I see ...

If she teamed up with Iku, wouldn't they be invincible?

Everyone wishes for yuri.

angrybull said:

Everyone wishes for yuri.

Considering who the persons she talked to, there's a very high probability that all this is fake. Everyone knows Marisa wants to steal things, Alice thinks about yuri, and Seiga to be less hated.

Marisa said:

She can read desires, but not the atmosphere?

So, pair Prince Shoutoku off with Iku?

I do wish Miko's ability came up more often in fan works, it seems like it has a lot of comedic potential.