From my standpoint Chromium packs need an overhaul and needs to be fixed. Check the Bugs forum and you can see it addressed in the Known Issues thread as well as a Chromium Pack thread that players are not getting full shards for characters when multiples drop sometimes. So Chromium buyers (F2P or P2P) are getting boned on them at this point.
Also, it seems the Chromium packs need to guarantee shards for characters you don't have, say at least 1 for a 4x and 2 for a 8x.
I am sure future updates will allow for the recycling of shards of unwanted characters at a heavy cost to shards for other characters. At least I hope so.
I have "invested" a good night or two out on crystals in this game so far. At times I feel it has been worth it and other times I have regretted my decision because of how terrible the packs can be.