Seems strong. The Eldar has access to quite a few psykers, even without the synergizing Fharenal and her pair of psyker-warlocks from The Final Gambit: the Destructor, the Spiritseer, both Farseers, Wroth and in an Eldorath setup there is even the Counsil..

And that's a nice command stall option too, exhausting the opponents promoted pirate or heavy hitter, rendering it unfit for either command or combat or both.

Could potentially prove to be a neat answer to Preemptive Barrage or ranged units buffed up on Catachans as well.

Very promising indeed. 

Probably because it will be used during combat more often than not.

I've read people treating it like a Suppressive Fire, but it has much wider action windows than the popular AM card.

Would you use it in the Deploy phase, allowing your opponent to compensate for it? If you're looking to win command Superiority is a better card. Using it in Command or HQ phase feels like minimal benefit.

Would you use it in the Deploy phase, allowing your opponent to compensate for it?

Allowing your opponent to compensate for it. Forcing your opponent to compensate for it. It's a fine line.

Would you use it in the Deploy phase, allowing your opponent to compensate for it? If you're looking to win command Superiority is a better card. Using it in Command or HQ phase feels like minimal benefit.

Well, FightingWalloon is not far off here I think: assuming you haven't yet passed, it might be used in the deploy-phase after the opponent has passed, both denying command presence and making the exhausted unit look bad in a potential fight at the same time.

Such use is probably one of the strengths of Mind War, its flexibility. 

Let's go back to comparing Mind War with Surpressive Fire:

SF costs 0, but you have to exhaust one of your units which has to be present on that planet. In a more "swarmy" deck this might not be a problem. Also you can target elites/uniques as long as it's not the opposing Warlord.

MW costs 1 but you need 1 Psyker army unit (! No, your Eldorath does not count) present on that planet. Doesnt work on elites.

I, myself, am someone who plays eldar only rarly but I face some in my meta. My experience is, that eldar both tend to have at least 1-3 ressources left (all the time...but then again I suck at building choke decks and my oponent mostly scores during command) and with the new units they get MW seems slighty better then SF to me.

Would you use it in the Deploy phase, allowing your opponent to compensate for it? If you're looking to win command Superiority is a better card. Using it in Command or HQ phase feels like minimal benefit.

Yes, I absolutely would.

Playing as a deploy action creates a delay, gives a command advantage, and gives you all the benefits of playing it during the combat phase... except surprise. If you play this during the Deploy Phase opposite a Starbane Council, you then force a hard decision on the opponent - if he command snipes your Starbane's Council, he then has seized initiative and has to exhaust himself opposite the Council, or flee. 

Also, there's a broader picture to consider that makes the deploy delay and command advantage more worthwhile than the combat surprise: Ssylth Mercenaries. Eldar have access to this excellent card, but its only an excellent card if you can generate enough Deploy Actions BEFORE you play the merc. With their heavy reliance on 3-cost Units, Eldar find this card a lot harder to play than say, DE or Chaos.

Any 1 or less cost deploy action of good quality - whether its unit, support or event - strengthens a deck's acceptance of Ssylth Mercenaries. 

Superiority, while being a card I very much like, suffers from the same problem as Foresight - it happens after the deploy phase is finished, so doesn't delay your Mercs.

Its not just for the sake of the mercs, of course, Biel Tan Guardians and Promotion love it when you can delay too. 

This card has become an easy 3x for my Eldorath/DE deck, and about half the time, I'm playing it as a deploy action.

I'm playing with 2x Mind War but I might add one more in. More exhaustion is always good, and even with its non-Elite restriction it's still a great card. It makes Starbane Council much more useful than a sig unit who needs their warlord present to be a threat. 

Experimenting this in non-Eldar factions at the moment. Given that I would justify 2+ in Eldorath with 4x Council and 3x Warlock Destructors, I figured that taking the Warlocks + 2/3x Prophetic Farseer + 1/2x Wroth would work in either Shadowsun or Morn. Yet to test out Shadowsun but it has worked quite well in Morn so far, especially given the level of control afforded by Archon's Terror and Klaviex. Plus, all of the Psyker units mentioned have 4+ hp, meaning they ain't dying anytime soon. 

I'm in that same boat, but it's very tricky to include in Shadowsun since finding free slots in her builds is quite difficult.

Both Kith and Morn have an easier time going that Psyker route.

I actually tried an all-exhaust deck with Silver Blade Avengers. It did not go well.

I don't think the Silver Blade Avengers are a good card, period. If they had less hp and costed less then maybe, but as they are they are just too expensive to be worth it in any deck.

As VonWibble has said, the high hp of the units definitely add to the deck since a single Aux Armour/Ion Rifle is enough to boost them to silly levels, thereby allowing for the attachments to be spread out rather than clumped. Plus, it provides some much needed control to a Shadowsun deck that's notably lacking any kind of answer to problem units (short of Doom / Exterminatus) without the timing restriction of Deception

This is gonna be much better once the new Eldar warlord is released.