Well from what I remember, the devices in the temple were some kind of locks or mechanisms that Rikku fiddled with to get to the Cloister or something.
And considering how Wakka reacted, and Auron's remark of "they betray their own teachings", it had to be pretty bad.

As for the Fayth Cluster, I really don't think anyone knew what was going on. Braska said point blank that he thought there was a chance Sin wouldn't come back...yet Yunalesca tells the party flatout that it will always come back. So obviouslY Braska and the other summoners didn't know this detail.

And the Cluster existed to summon Dream Zanarkand I thought. I just wondered if Auron or anyone else knew that.