This. I do play a trickster rogue, but I will always try to cap before combat. Then when I get into combat I target their necessary classes, firstly the healers, get those down asap because no heals means the rest of the team can mop up the dying. It's more about strategy and picking your battles. When you get swamped by…
Here's a workaround, not a fix unfortunately, you can mail yourself the lockbox stack you have and just never claim the mail. When you get more boxes, claim the stack from mail, then remail the combined stack to yourself. Rinse, repeat. Annoying, but at least you're not occupying an inv or bank slot for more useful items.