OK Eldar players, I thought I would chime in on the new Farseer, because he is a new level of awesome sauce that I have not heard too many people talking about yet. He is cheap, cheap, and full of useful powers and options through his psychic abilities.
Lets get down to it and do it quickly.
Runes of Warding: Now allow a +2 to your deny the witch roll. This will often mean that psychic powers will rarely effect a unit with your Farseer in it.
Runes of Witnessing: Now allow the farseer to re-roll a psychic test one use only.
Ghosthelm: The farseer can expend one warp charge point to prevent perils of the warp damage.
Singing Spear: 12" S9 AP- Assault 1, fleshbane
or S:user AP- Melee, Armourbane, Fleshbane
He comes in rune armour which gives a 4+ invul save, but the most exciting is that he starts off as a level 3 psyker for his base 100pts. This is cheap for what you are getting, which is access to Divination, Runes of Fate (eldar psychic powers), and Telepathy.
The primaris power for Runes of Fate is the trick here, its Guide, has a 24" range, and effects all friendly units.
So yes, you take your Farseer, take the primaris power Guide from Runes of Fate, and then take Divination and take the primaris power prescience, and suddenly for each Farseer, you can make two units re-roll their shooting attacks. (note that Guide is 24" and effects only shooting, while prescience is 12" and effects all failed to hit rolls).
Now that Eldar are mostly a BS 4 army, you can make any friendly unit (Dark Eldar or Tau included) re-roll their shooting attacks.
The Farseer is much more flexible than just this use, as you can take two farseers to make sure that you also get a good chance at getting your fortune.
So yes, I see the Farseer much improved over the last version. The new codex is opening more opportunities that are hitting the tabletops as we speak.