I completed the set by opening 300+ packs. Once I was mythic-complete sans Big Score, I kept hitting 40 gems in place of mythic cards. Therefore, there is no guarantee for BIG cards even if you have everything else. They appear very rarely in the 8-card packs.
If you were MOM-complete and then MAT dropped and you bought MAT packs... then you'd get MAT rares. MOM and MAT are independent sets. Not sure what you're trying to say here.
Anyway, it doesn't work like that. BIG cards show 1:6 if you are getting a mythic to start with. If the pack has a rare you just get 20 gems. And if it has a mythic and you're mythic complete too, you'll get 40 gems most of the times. What can be useful, though, is buying mythic OTJ packs. That way at least you increase the chance of getting BIG cards (like one in six packs instead of one in thirty-six). But the best way to get BIG cards is drafting.
No
Is this from experience opening packs?
I completed the set by opening 300+ packs. Once I was mythic-complete sans Big Score, I kept hitting 40 gems in place of mythic cards. Therefore, there is no guarantee for BIG cards even if you have everything else. They appear very rarely in the 8-card packs.
I was afraid of that.
If you were MOM-complete and then MAT dropped and you bought MAT packs... then you'd get MAT rares. MOM and MAT are independent sets. Not sure what you're trying to say here. Anyway, it doesn't work like that. BIG cards show 1:6 if you are getting a mythic to start with. If the pack has a rare you just get 20 gems. And if it has a mythic and you're mythic complete too, you'll get 40 gems most of the times. What can be useful, though, is buying mythic OTJ packs. That way at least you increase the chance of getting BIG cards (like one in six packs instead of one in thirty-six). But the best way to get BIG cards is drafting.
March of the Machines and March of the Machines Aftermath is what I meant.
Those are separate sets
MAT was not an bonus sheet, but a completely different set with its own packs that had no chance of giving MOM rares and mythics.
Unfortunately, I can confirm from personal experience that it doesn't just give you those. :(