There are two logistical annoyances that I want streamlined.
First, if I log on and want to make myself available to anyone who needs any of my characters, I'm out of luck. There are workarounds. I can look through the LFMs and send a tell saying, "Yes, I have a level 15 wizard; let me switch". I can also make sure my guildies know what characters I have. The first work-around requires that I find the party; a party leader cannot find me, even if I want to be find-able. The second workaround makes me available to only a small number of people. I want the option to show up in the social panel as ANY of my characters.
Second, I want to be able to look through the inventories and banks of all my characters at once. I have many items in storage, either because they're useful for leveling or because I like having stuff to trade. In both cases and especially in the second case, it's a nuisance to have to log in and out over and over to find that darned <insert item> that I might or might not own.
The workaround here, of course, is that I organize my characters' inventories and banks. This is stupid. I'm paying to be able to fight monsters in dungeons. I understand that inventory management is a necessary logistical exercise. That doesn't mean it shouldn't be streamlined. Make it easier for me to manage my inventories so that I can spend more time helping my fellow players get through dungeons.
What I suggest is this:
An omni-login. Let me be on as all my characters at once. Let me access all my banks and inventories, and let me show up on the social panel as whichever characters I'd be willing to play.
Also, add an auto-sort feature to inventories and banks. I know the game can sort stuff; my Sell list mysteriously comes up in a particular sorted order no matter the order of the stuff in my inventory.