I have noticed that when you level up and get a free card (which is very generous of the devs to have in place and i really appreciate) you can get cards even if you have 3 of the mythic versions of that card. Is this intended or is this a bug?
I don’t think it’s a bug. Mythic cards are something extra and aren’t counted towards anything. Just like if you have 3 standard copies of a card and a mythic copy the system won’t auto disenchant your mythic copy.
Mythic cards are counted separately - for example, if you get your first Mythic in a Battle Chest when you already have 3 ordinary copies of the card, it will appear as “NEW”.
Obviously this is a very marginal concern since most people who have 3 of any Mythic can probably get 3 of any normal card (of similar rarity) very easily - but in my own opinion, I like the current system of counting Mythics separately. If I own 3 Mythics but no Normals, and I get a Normal, I now have the option to disenchant the Mythic and come out ahead on Faeria (or in the worst case scenario I can disenchant the Normal which is not that bad either).