Since Kickstarter the engine development has been fragmented and that's how it stands. Most things taking a direction and changing as part of the ongoing "evolving" theme to development, which has slowed down all things towards a mature development. This may continue for a long time yet...
At the moment AI is limited partly because of what's hard coded and the reliance on all the other things that need to be in place which the AI may require and which may affect/influence it for better or for worse. Everything from physics to obstacle avoidance, pathfinding and behaviours and most of these things and many more can be of differing qualities (simple or advanced) and can make a massive difference and all which may affect the quality of AI itself during gameplay. Other things like engine Performance and efficiency too can impact on the AI and it's behaviour when a lot of AI activity is happening at once.
Hopefully the road ahead is now or will become a little smoother once Direct X11 is in place. Of course many things which AI (and other things) might best require to be in place are themselves likely to be fragmented in coming along as the road map is still fragmented by development direction and user preferences (voting) so some things may be in place sooner than others. This is the way it has been and may well continue and is why perhaps many see various features as unfinished - because they perhaps are depending upon what is envisaged/expected by the developers and users and their priorities, which may vary widely.
Most main features to date indeed perhaps could be said to be under developed, water, terrain and so on, some of everything perhaps being better than nothing so more people half something of what they want or need. Quantity Vs Quality?
The AI currently is to say the least basic but better than you may get and have seen out of the box elsewhere. That does not necessarily mean it could not be a lot better by the will of both the developers and the users.
Apparently Bots Navigating will be possibly receiving attention "soon". At least that may provide the basics of that but any more may take much longer as good AI requires somewhat more than that.
Quote: "AI seems to have most of the necessary functions and data available in the lua"
Some of the default current AI scripts do have a variety of behaviors which at the moment do not seem to work, work at all or work well or correctly and have performed somewhat better previously, e.g. go home or run away if health is low, pathfinding itself is hit and miss over entities or terrain due to engine changes/restrictions currently....
A lot could be potentially improved and or added/extended perhaps if as said the developers and users wish it to be so. e.g. advanced pathfinding/nodes/entities to control/manage AI behaviors, random behaviour choices, character lip sync and so on. Characters themselves have an animation set largely untouched and unused - excluding lip sync of course which may never see the light of day at least any time soon....
Many may be very happy with basic AI and have no need/want of anything more.
Not sure what can or should be expected by users in particular in a product where the cost to them might now be described as a giveaway or so it seems to me in the case of the base product irrelevant of any other engine considerations. That is a developer decision and obviously/presumably impacts upon to some extent what one could realistically expect in return, or perhaps not. I don't know...
Happy 2016 game making all.
System : Advent Windows 7 Home Premium 64bit. Intel(R). i5-2310 CPU @ 2.90GHz. 8.00 GB RAM DDR3. Storage : 1389 GB : 1088 GB Free (1389 GB Total). Graphics : NVIDIA GeForce GT 530. Total Available Graphics Memory : 4095 MB. Dedicated : 1024 MB. Shared : 3071 MB. Direct X10