I have two issues with current portal implementation.
Create a portal in game area, walk through it, end up in town. The portal is not only not where you appeared, it is off-screen; in most cases I’ve seen, it is off the minimap. So returning via the portal means you have to first find the bloody thing. Why not have the portal right beside where you materialize?
Create a portal in game area while surrounded by aggroed mobs, walk through it to get to town, find the damned portal, walk through it to get back into the map. The mobs you left are still clustered around the portal, they are fully aggroed, and they hit you immediately. I have been taking damage while the screen change happens; I’ll finally get control of my char with about 50% of my life gone. Please consider adding the short invulnerability phase you currently use when entering an area from an adjacent area.
There are a lot of bugs related to portals right now that will no doubt be fixed. However…
There is zero reason you need to portal to town while progressing midway through a zone that you need to return to. One of the mistakes a lot of new players make is thinking they should be picking up all the loot and going to town to sell it. Don’t do this. The devs intentionally designed loot to be value less. You are actually making less gold per hour doing this than if you just left all the loot on the ground. Later in the game you’ll see piles of gold in the thousands while loot is worth like 5 gold to sell.
If you have side quests to turn in, wait. There are lots of waypoints in the campaign if you want to return to town to turn in a quest, or just wait till you get to the next town. You aren’t really missing out ever waiting to turn in a quest. You really should never have to stop midway during progression, just keep going. You’ll avoid all the portal bugs because honestly… you never return through them. You only use portals one way normally.