I think it’ s even more random (lucky) then what I’ve read on here, at least from my personal experience. I’ve only been playing GoW for about 5 weeks or so, and now I’m around level 123 or so. My wife started playing the same day, and is somewhere around lvl 110 or so. She has opened even more chest then I have, and she now has only 3 Legendary troops total. … At the same time, I have 9 different Legendary troops, with copies of two or three of them, putting me around 12 or 13 in total.
Also, only 1 of my Legendary’s came from a Magic Key, which I’ve only had about 8 of now. (Purchased maybe 3 in the first week or so, but only win them now in TH) The rest of the Legendary’s all came from Iron keys. … We joke about this, and the wife gets so mad each time I get any new ones. So yeah, I think luck plays a big part.