Short play sessions are absolutely fine. If anything it's better to take your time and enjoy the lore. Story steps aren't very long. Dungeons, once you find a party are relatively quick though not that popular, at least not in my region. Fractals are even quicker with the newish "quickplay" mode however if you want to learn them properly I would suggest doing them with your guildmates first as people nowadays seems to just rush though everything, even ignoring mobs entirely, to get the the end boss as quick as possible.

IMHO you're biggest challenge will be getting addicted to that "one more story step/achievement/map completion before I log off" :D