There are few things that require 5/5 to scry/dig. Seems to be mostly furniture. I haven't gone for any mythic items myself yet, but it seems most (if not all) only require 4/5 -- level 7 scrying, I believe.
Do you mean you got a lead to a mythic item?
You need 5/5 to dig it up, you can get leads regardless of skill.
You get leads even if you don't own Greymoor at all and can't dig up anything.