@Gabrosin - finally RL let me answer your posts.
Events - I do not know how easy it is to create an event, but however much I like The Dragon War, my opinion is that not all event have to be as intricate as TDW. I think that there should be more puzzles in MTGPQ. So small levels, like story mode levels and small events without special support effects, is desired. BUT these should be sprinkled with highly intricate events similar to TDW.
XP and card usage - since I have no clue how the XP-system is going to work I am hesitant to speculate, but I fail to see how that will have any impact on card usage. But I’ll get back to card usage.
solution 1 shorter set rotation - when I read this, I thought you are on to something! However on second thought I’m not sure. Because with faster rotation I expect it will result in sloppiness in regard to card balance. If you release a poorly balanced card, similar to BSZ, the developers can just shrug their shoulders and say the card will rotate out in a year. With a 2+ year they have to have a bigger focus on card balance.
solution 2 Planeswalker rotation - I strongly dislike this idea! I hope this never get implemented. It promotes laziness, if the PW is to strong then the devs. just shrug their shoulders and wait for it to rotate out.
I think that what should be considered instead is to make more events that are couple to specific PW or to mono-coloured PW. So when an PW-event is run, D3 could have a bundle in the vault with the necessary PW plus card bundles which are matching the PW to get players started. Players can choose not to pay, but then compete at a disadvantage.
Solution 3 varied deck lists - intriguing idea, which I think will be very difficult to develop so the generated decks are interesting to play against. I think that rotating the creatures could be a middle way that would be easy to start with, but maybe not.
solution 4 varied secondaries - great idea. This might be able to help the developers make new events quicker, but I do not know how much development that would require. Just make a list of all the secondaries and roll a die to decide which secondaries are in the level.