Yep, put this idea forward a couple of times in other threads.

These units should stay and fight until every enemy is annihilated or until they die. Alternativly they could lose the berserk effect if too low (regaining consciousness over the massacre).

While certainly not the most pressing matter at hand and not necessarily noticeable (unless playing as Trogs or fighting them), this would really add consistency to the game.

Yes I agree that the most reasonable option would have these units fighting to their death

I fishined Xcom:EU several times, watched some playthrough as well from the older version and the latest released version.

Ever played Warhammer? There was an ability called frenzy. Basically the "berserk"  we have, except you would lose its benefit when your unit would "lose a round of combat" to make things simple. Was merely pointing out at an alternative.

Berserk is one of the changes I like the most in LH.

Sounds like a great idea for a different spell. 

Panic - +25% initiative, the unit becomes completely uncontrollable, can target any unit, and takes a random action each turn while under the effect.  25% bash (self) chance each turn.  Unit has a chance to resist each turn.  Lasts for five turns.

How painful would it be to have the AI cast Panic on your unit and have him turn around and start hacking at your other units.  They have "Fear" but that's an initiative hit.  I would love for "Fear" to have a chance to proc "Panic" which would make any monster with "Fear" very scary.  As your entire army ends up randomly quivering on the ground, retreating, or attacking wildly.

Bezerk should definitely not retreat.