I made a video on how Guilds will very likely exploit this feature:
https://www.youtube.com/watch?v=fEeOmgwWSDo&feature=youtu.be
In a nutshell, even if you limit how many times a character can fast travel per day, top guilds will still require, and it will be meta for endgame, for you to have 8 accounts. So you will have 8 strong characters, and even if cooldown was 1 week, one of your characters can teleport to any of 7 locations you want every day.
In my experience every time you try to make a catch-up mechanic for casuals, the hardcore utilize the system far more prolifically and leave behind casuals even more than if the system didn't exist. XP pots, when they were proposed, the devs pitched them as so expensive only rich business execs would use them; we all know where that went.