Armory:

I had a conversation with a friend recently who kept asking what class I was taking to lvl 80 next, and I kept telling him I wasn't. I was taking every class to 70, and not because they are the classes I want to play at the time. By the time I hit Heavensward it was clear to me that I had two options; 1 pass on everything except gear for the class I'm leveling at the moment, or 2 Organize what classes I was lvling in groups that share armor so as to toss the old gear asap, and dedicate retainers to equipment storage. In the long run the 2nd option means having better gear along the way and less inventory management in the long term, so I took each class to 50 in groups, then 60, now 70, keeping all gear over the threshold (aside from main) on a retainer, and for a while it looked like 2 retainers might not be enough even then. Even with an organized approach two sections of the armory remain a constant problem, mainhand and rings. With every class unlocked almost the entire mainhand page is used up with equipped items, and since two rings can be worn it needs double the space of other pages. The obvious solution would be to increase the number of slots for each category, but that will only last until even more classes and gear are introduced and it becomes a hassle again.

Here's an idea, one that admittedly would take a lot of work and turn a lot of things on their head, but bear with me. What if instead of an armory all gear was turned into an unlockable, kind of like miniatures and mounts. Consume the gear and have eternal access to it for other classes and cosmetics. This would also render the armory and glamour box unnecessary. It would also be nice if glamours could go by class rather than by gear, so your PLD and your DRK don't have to wear the same outfit, would be the perfect time for such a change. Most importantly, it will remove the hassle of inventory management from gear. On a side note, it would also give an incentive to unlock gear from old raids etc. instead of just being more clutter to deal with.

Raid materials:

If both of the other solutions are implemented this will be less of an issue. At present, all the different 'turn in' items from raids and other endeavors aggravate the inventory issue, and I suspect it's intentional (gotta sell more retainers…). Turning these items into currency would definitely help the situation. Regardless, most of these items besides the most recent get tossed because it's just a hassle due to inventory management, which means less interest in old content.