I got a Mythic Legendary today and the number went up by less than 100 when I expect it to rise by 400 (disechant price for Mythic Legendary).
But I didn’t actually disenchant it so not sure if it’s actually going to disenchant the mythic or normal duplicates. Can someone confirm please? It may be a text bug, I don’t know.
It doesn’t disenchant either.
I don’t understand. It must disenchant one of the them if you have more than 3 (or 1 for Legendary), right?
A mythic card is not the same as an ordinary card and does not count towards excess. It would be really awful if they did, say, if you were trying to build up full mythic collection.
It’s not quite that it doesn’t count towards excess. It does - but towards excess of these mythic cards.
From game perspective a X Card and a X Mythic Card are two completely different card. Just like Y card wont disenchant if you have 4 X cards, X Mythic card won’t when you have 4 X cards.
Ordinary cards and their mythic versions count as 2 separate cards. So you need to “Show Mythics” and disenchant them separately.
Also, I think the restriction is "One of each Legendaryper deck, which is not the same as one per collection
It actually is. The deck limit is the exact thing that defines what a collection is. A full collection is a set of cards that allow you to make any possible deck - and thus a limit on deck translates into a limit on full collection.
Thanks everyone. I understand how it works now, thanks for clarifying. 
I remember now - cards can be re-used, so you are right 
