The fragment system is a pretty good way to handle gaining new cards, and since the introduction of it i have really liked it as a fairly fair system.
Here is my one suggestion to the fragment system: Put the number of fragments you own next to your credits in the main menu
Why make such a small, minute change? So ive recently got my brother to try this game out, and hes played it for about a week and he pointed this out to me: "Why are fragments hidden away? Crafting is meant to be a big thing in the game, its like the only way to get good cards, so why cant you see them alongside the credits etc." It never even occurred to me, but why are the fragments hidden away in the recycle/craft menu's? Shouldn't they be at the forefront like the other currency (soon to be currencies?) just for simplicity's sake? Fragments are only credits but crafting only. It would be less confusing to have everything you have be up at the top, and to be honest it just feels a bit tacky, as if they forgot to integrate it into the header in the first place.
On a side note, wouldn't it be better to just give people the fragment rewards along with the credits? You get a case every match, and you cant even open the case, so why not just average the reward out and give a flat amount after a match? I have never once been given the highest amount to get in a fragment case and went "wow", half the time i do not even acknowledge the reward.
Tbh i got both of these changes from Paladins, because as much as that games cosmetic and shop system is a bit convoluted, at least i can see what i earned from each match with ease and see myself progress.