Haven't seen this one mentioned anywhere, so thought I'd post it up before I forgot about it.
Last night, I triggered a fight with a large bunch of orcs (the one which I believe Larian posted about another group of players luring through town until almost everyone in cyseal had been mercilessly slaughtered)
I hadn't intended to trigger it, and just wanted to get away, as I was a couple of levels too low for the encounter and hadn't picked up any henchies/companions to help out.
Much like the adventurers in the article, I ran back to town. Roderick dropped in a dramatic last stand against an orc shaman that took them both out, but served to prevent the horde from healing itself, and Scarlet (in archer mode) legged it back to town, applying liberal amounts of "scorched earth" to try and hold back the orcs, or slow them/whittle them down a bit.
Got back to town and opened the gates. Stepped through, then closed them again, figuring they might buy me some time.
They bought me all the time I could ever have wanted.
I found that on closing the doors, the orcs would lose sight of me. I was still in combat range, and was held "in combat" but the orcs wouldn't move, attack or do anything else.
I realised that if I stood in the right spot and that I never let myself run out of AP (and so trigger the end of my turn) I could open the gate and fire at the orcs with impunity. Every time I ran low on AP, I'd just close the door, end my turn and wait for a fresh batch of AP so that I could repeat the process all over again.
Leaving the door open between turns allowed me to "pull" orcs towards the door, and provided I never let them get inside the gate, I was basically safe to pelt them with no problems.
Unsure how you'd correct for this... Possibly apply an AP cost to opening doors, AND allow creatures to move to the last spot a player character was visible from, if they suddenly break LoS or something.
For the TL;DR folks - if you hide behind a door, and never let your AP gauge empty completely, a ranged character can open the door, shoot targets and then close it again before the end of their turn to avoid being targeted or hit by enemies.
Anyhoos, hope it helps.