Medikit only "fixes" fatal wounds, it doesn't actually "heal"... and vanilla aliens cannot bleed, so there was no need to add such AI feature.
Modded "aliens" usually can bleed... but adding such a feature in my opinion is against their interests... instead of shooting at xcom, they would run to their wounded comrades to heal them and get killed themselves.
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You can see this "smart AI abuse" very well in xcom2012:
- if you let's say suppress an enemy, it doesn't care what the other xcom soldiers do, it always fires back at the suppressor, or hunkers down or something... never shoots at other people... even if they are flanked and just a few tiles away
- or EXALT medics pointlessly healing themselves or their comrades just to get killed next turn... instead of shooting at xcom
When you know a little bit how AI in xcom2012 works... it is RIDICULOUSLY easy to avoid getting hurt... you can abuse the shit out of AI being "too smart".