in the near future we'll introduce a small balance change for Teleport. The reason is that Teleport has to make the caster ethereal for a short duration to break the aggro (without it Teleport feels very bad). The drawback of this solution is that it can be exploited by spamming Teleport which makes you more or less invincible.
To prevent this exploit we will introduce a Mana system for the Teleport spell. You get a specific Mana threshold and a passive Mana regeneration. Each use of the Teleport spell consumes some Mana and the spell fails if you don't have enough Mana left. In comparions to a cooldown on Teleport this has the advantage that you can spam the spell for a while but not infinitly. That way we can probably prevent exploitation without making a dynamic playstyle impossible.
Details on the numbers will be posted here when I am done. The initial numbers probably won't be the final ones though. We will play around with it a bit and adjust things if neccessary.