This mouth wasn't a foil, but yes, 1 foil per 7 packs (which is what the pack lists as approximate frequency) means that I should have found 2.28 foils so far, and I've found 3, so that is a little more frequent than normal.
Of the foils, 1 (Balrog) is masterworks and the other two (Gandalf, Witch-King) are RF. I haven't found stats for how many of the foils should come up as masterworks.