I have in idea on the tutorials, idk if its possible Amon with the type of system istaria is run on. but... a lot of players dont read the blue pop ups :/ i know this from a few years ago trying to get some of my friends into this mmo.
anyways i'll get right to the point.
if you can manage some sort of short video showing how to use "said" controls.
(Example) small video, dragon dies, up close view of recall button. dragon is revived. end of story.
(Example) small video, Auto open C window showing the list of ability icons, Mouse cursor appears on screen, displaying a drag and drop motion with the ability icon onto the hotkey bar.
ECT
I don't know *Shrugs* just an idea.
to me it would make the game seem a bit more interactive with the players
could work for explaining how biped classes work as well
Or new idea! this one may be less invasive to the players.
you could have a "Guide" tutorial. show them around the game interface a bit with a guide,
highlight buttons and tabs on the screen encouraging the players click on them, follow the tutorial.
could work with a little bit of all 3 styles of tutorial, little high lighted button here, short video there, and a pop up bubble to explain more complex things..
I'm probably rambling by now, no idea if this was of any help or inspiration. i hope you find a solution Istaria is a wonderful mmo and i hope it stays alive for a long time to come