The real long term problem with Destiny and balance is the lack of economy. You get 2 resources/mana per turn. FFG stated Game of Thrones 1.0 was hard to balance on a 5 point scale and increased the gold curve up to a 7/8 point curve. Cards in Destiny must cost 0%, 50%, 100%, 150%, 200% or 250% of your resources per turn. It's really hard to balance upgrades when 0, 1, 2, 3 are your only choices. How many 5 cost cards see regular play, or 4 cost? Upgrades with dice need to neatly fit near a 1 or 2 or 3 value. Say a card should be a 1.5 it must either be rounded up or down. As a 1 it might be a tier one go in all decks card. As a 2 it will be just another binder card. Long term I don't think there can lots of variety balanced on such a small scale. If we got 5 or 10 resources per turn you could much better balance things. If the cards were all balanced it might make for a boring game, but the competitive card pool would be much larger.
Magic works so well as you generate mana(resources) equal to the turn number. The game grows with potential each turn longer it lasts. Destiny has a small ramp up into turn 2 or 3 then we start ramping down as character die off.