XLN drop rates were initially fine (1.26%; this is the expected mythic drop rate per card in normal packs), but you are correct in that for the majority of the time XLN has been available, drop rates were indeed rubbish (0.57%).
If you combine that with the fact that RIX drop rates were initially great (1.95%) and are now good (1.43%), and DOM drop rates have only ever been good (1.54%), your owned mythics per set aren’t a huge surprise.
Note however that something’s already been done about XLN; drop rates have been decent again (1.25%) since the DOM release. So your XLN collection is likely to improve at a better rate than before, if you keep opening packs regularly.
These quoted numbers are according to the published drop rates, and they’re also reflected in the pack opening data that we have in the community spreadsheet (though at the per-set, per-version level there’s not a huge amount of data). And as always, individual luck will still vary of course.
I still can’t understand for the life of me why oh why no masterpieces are available in regular ILX and RIX card packs. It is the only set in the game where this has been done.
The way it appears to me, it is a thoughtless and careless mistake that should have been fixed long ago - along with the horrendously weird drop rates. (I ended up crafting all the mythics in this set - not even worth the frustration of getting a guaranteed common and uncommon premium pack).
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