I agree pretty well with covaithe - might've gone a little too far in nerfing the communication.

I like the idea of having the communication stable within a locality, but more unpredictable outside of that. I also like the idea that the communication requires performing a ritual which either a) can only be performed during some sort of celestial phenomenon, or, b) works better during a similar phenomenon. Perhaps the ritual requires a celestial phenomenon to be stable with communication between different rituals?