[tinkthank]

Just playing my first game of Arco (thought I would try out some races I have never used before), and it took me 6 turns to get a Mystic without all three random paths stacking. (That is, I recruited a w3, w3, e3, w3, f3, e2a1 Mystic in that order.) Until I got the e2a1 mystic, I was about ready to think that the elementals ALWAYS stack.
I am obviously both stupid and have bizarre luck. (It took me 10 months to get a Starspawn with 2 stacking randoms and I still dont understand the formula.)
Can someone please list here the formula for figuring out the chances of things like this? I had stats back in high school but since then I have left the field of natural sciences and moved into the armchair humanities, and I just dont get it.
Is it something like 7/8*7/8*7/8 for the mystics? Damn, sorry, and thanks in advance.