I think portal system is huge mistake. It is too "gamey" and don't have good enough explanation.
It is just absurd how even in Act I we see how people died trying to deliver some letters. Why didn't he travel by portal? And lorewise it is wrong too.
Fast travel mechanics is convinient and super cool to have in this game. But it must be implemented differently. I like the idea with signposts and message - "You traveled for 1 hour".
