I too have experienced nothing but increased lag with each new set.
When I first started playing MTGA it was pretty smooth but now it is extreme lag all of the time. This is not my PC or internet connection, it is your game. Stop being so cheap and fix the issues WoTC.
Again, performance issues are VERY hard to pinpoint/reproduce. Please report them so we can look into it and be as specific as you can. Saying "my performance is worse, fix the issues" doesn't tell us anything.