I had a character that I had disabled XP for. She was level 15 in Praetoria, Imperial City. That's the level cap, and I was progressing through the storylines there. I took a break for the evening and then came back home and was planning to log on for an hour. I completed Beholder's story arc and suddenly leveled up, and thus instantly lost access to all the story arcs I wanted to do in Imperial City. When I turned XP off, I was *very careful* about it, and hit Apply. I log back on, and it's "helpfully" reset to back on again. So now I'll have to delete this character and start all over again. All that time and INF, down the drain.
I dearly want to know how to *keep* XP turned off. Clearly I'll have to double-check it *every single mission* from now on. What a pain...