I'm not entirely sure where this all came from, but I shall try to address the comments sequentially as much as I'm able. One must also remember that
Tir'asur is a world which will not be developed for a world... If I cannot at present find the time to produce the 'example of world creation' for the Anargo capital, I don't think that it would be fair to shift to another!
The purpose of Tir'Asur... I'm afraid colonies do actually crop up 'just for the hell of it'. There are enough real-world analogues for that. In direct terms, however, the name of the world - Land of the Phoenix - is a reference to the fact that the Phoenix Clan was initially responsible for colonisation of the Maiden World as an adjunct to the 'home' craftworld. Why? Why do eldar colonise in the first place (remember not everything revolves around the damned wargame!)...?
I could quite readily tell you that the world is partially there to form a node in the weaving of the Metarune... but that would be fairly meaningless to most. Annoying to others who don't like fan 'fluff' impinging upon their beloved universe.
Talking about tactical situations at the moment is fairly spurious since it is not located. The only 'high-tech' world of sufficient naturally-rolled TL to locate the eldar colony world is, once again, right on the edge of the sector. For this reason alone I'm wary of using that world, but rather going for one in the centre. To repeat myself I have not selected that world...
However, given that the world is not going to have significant military resources as a 'standing force', then it would seem daft for them to have an overt tactical significance.
Watch station... The eldar do not, for the most part, need one. Eldar precognitive abilities - my god, the Farseers are used for everything else - are capable of this on their own. The purpose of the world is as much symbolic as anything else. A living recreation of some aspects of the old homeworlds, a place where eldar can go to feel natural gravity, the rolling of the atmosphere and other such things. It is a place where they may make contact with the primeval essence of their race...
So malika, you can stop obsessing about the 'small dock' that you have mentioned oodles of time.
Tir'Asur is not in the 'present' of the Anargo sector - whatever that might be decided at, since people are for some reason keen on setting it in the comfortable past - a military outpost, whether that is a 'watch' or a 'army' outpost.
Necrons... No, they will not be dominating the sector. Neither will the Aoideans. That they will be a part of the puzzle is unquestioned, but '<insert race>-centrism' isn't something that I'm overtly fond of.
"Spirit Stone-controlled weapon systems..." Yes, the eldar are capable of that. There will be, as with all craftworlds and even Exodite worlds, a micro-net/Infinity Circuit. Ancestors will be free to move between systems at will so, yes, they can control systems. This is, after all, an essential part of the 'fluff' on eldar engineering and control systems, as well as being mentioned in early WDs such as 115.
Again, though,
Tir'Asur is not a military colony and will not be bristling with orbital defence weaponry, standing armies, standing fleets or even oodles of hyper-sensitive electromagnetic sensors (or 'listening warlocks') to form a 'watch station'. It is a 'peaceful' colon that is merely a stepping stone to the future goals of the eldar...
"... so perhaps no-one knows the eldar base is there..." No-one knows anyway, you don't need to recourse to a 'holo-field' generator.
I'm really intrigued at the input, but all of it is trying to set up a 'peaceful' colony world as a prelude to significant eldar presence, or as an excuse to put it there. Eldar presence
may expand depending on the advancement of the Necron storyline...
It exists to exist, a first stepping stone by the 'returnist' eldar, those that follow the Phoenix and the Spider. The Dragon only has a minor presence, which is why the world is not a bristling war-world (and another reason why it is definitely not going to be related to Biel-Tann)...
Kage