MArcomage

Cost: 1B
If Tower was damaged during opponent's last round
Tower: +7
else
Tower: +2

If u use this card after Quick card - it will add +2 tower even if ur tower was damaged.
Is it right or a bug?

You have to play it as a first card in your round (you can't play it after quick or swift cards to get tower +7).

But why for example Time Lock, which is also based on opponent's last round, applies the -12 stock (and not the -5) after a quick card played?

Because it's based on different data. Time lock uses opponent's card history, not changes on game attributes.