At least on DOMINATING.
The problem: by using a combination of root/stun/incapacitate/freeze on an enemy in the doorway, player can effectively prevent ANY number of enemies from being able to attack in ANY way because they can't get pass the immobilized target in the doorway. However, since there are no readied actions or overwatch mechanic, the player is still perfectly able to attack the enemies (by going into line of sight at the start of the turn and hiding behind cover at the end of the turn). This effectively makes player invulnerable.
Why this is
really bad: with proper rotation of immobilization effects (most easily achieved by psion or trapper, but practically any build can pull it off to some degree), there is no limit to how long you can keep the doorway choked, or how many enemies you can control this way. Having a single target permanently immobilized is already somewhat of an issue, but the
REAL problem is that it effectively makes it so that immobilizing ONE enemy is the same as immobilizing ALL of them. This makes combat hilariously easy and risk-free even of dominating.
Potential solutions:
1) Give all mobs an ability to push immobilized targets, give mobs capable of advanced item manipulation (those that can open doors) an ability to switch places with immobilized targets. Something like 20 AP action to push/switch places with a target of smaller size (human pushing a dog, etc), 50 AP with a with a target of the same size (human pushing human) and impossible with target that is much larger/heavier (human vs industrial bot). Maybe only enable this on higher difficulties (looking at you, dominating).
2) Improve mobs AI to the point where they don't fall for that (seems extremely unlikely to be actually possible to code, but
theoretically it would work).
3) Remove choke-points from most maps or make enemies capable of taking down walls (another unlikely solution because this would require a great amount go map re-design).
P.S. While we are at it, force field also needs to be looked at for similar reasons, see:
https://steamcommunity.com/app/250520/discussions/0/1744480967004247900/