I think the Quest Potions are risky, but definitely the best potential investment of 7.50 into the game.
You're getting 5x the chances to get special legendaries, epics, and cards are at an all time high. If you earn just 1 Card each day, and 100 DEC from those 5 chests, you've made back your investment. any card. That, is of course, if you decided that Potions have 0 Value. If you value potions and plan to buy packs, you will almost definitely profit in the long run.
There will be absolutely days where you go negative, but all it takes is one Legendary, 1 Gold Foil, 1 2000 DEC reward and you're suddenly netting positive for the investment.
Assuming you buy them with Credits of course :P
Interesting. I was just thinking that it is more fun to open 5 chests than 1 since I know that I will be doing my daily quests at least while I'm super pumped on the game. Who knows if I'll still like it in a couple of weeks.