People have done some math and found that even if you only get/do the Challenges that reward the least amount of Points, you still will earn enough to get everything (I believe this is for both the Free Tome and the Premium version).I think it would be interesting at the end of the season to see the numbers of people that actually redeemed any of the scrolls stuff in the premium line. Unless you just have a ton of extra currency with nothing else to spend it on, but at the rate it feels like I am getting it. Not sure there will even be enough to get all the items by the end of the season
Also something to keep in mind is that new players coming into the game won't have stockpiles of the Scrolls like those of who've been around for years have been. Same with the Research Scrolls. And even older players might have characters that don't have a lot of Wayshrines unlocked. Adding more chances to get these items isn't exactly a bad thing, especially since trying to fill up all the Premium slots with only Cosmetics would alienate a lot of players and also be a LOT of work for the devs.
And because I feel like someone might mention "oh but Crown Crates", you can buy Crate items with Seals and Crown Gems, they aren't only available from paying money every time you want something from any given Crate Season.
There's making something worth the money and then there's punishing people for not paying the money.