Pair tournament 800pts list - Ynnari Reapers

I am ahead of tournament in pairs 2x800pts. Max three detachments per pair, max 2 flyiers. I am playingwith Tau, he will probably bing Stormsurge. I was thinkng of a Ynnari gunline:

Yvraine
Autarch (for sweet rerols of 1)
8 Reapers + Exarch with tempest launcher
5 Reapers + Exarch with tempest launcher
5 Reapers + Exarch with tempest launcher

I am afraid of opponents alfa strike? Any thoughts and sugestions?

Alpha strike is a large problem in the current setup you have. Depending on what your ally brings, and on what missions you play. and if you roll for first turn or not etc.
I think you might wish to have a squad or 2 of throw away units. It can help PfD and help protect your otherwise vurnerable reapers.
While it sounds silly, just 2/3 squads of 5 plain foot kabalites or some beasts can do the trick. this will probably only set you back about 70 points and can greatly improve the survivability of your reapers.

Other than 1 Word of the Phoenix from Yvraine, I'm not sure where you would be getting your Soulbursts from. I assume you don't want your Reapers within 7" of the enemy so when they kill something they won't benefit from SfD.

You both are right. So maybe something like this:

Yvraine
5 Kabalites
8 Reapers + Exarch with tempest launcher
7 Reapers + Exarch with tempest launcher

Farseer
5 Rangers

This way I get the possibility to counter deepstrike with Forewarned strategem.

Coordinate with your partner if you can. With that few points, each of you is going to be able to pick one or two things to do.

Correct me if I'm wrong here as I don't play Ynnari (yet), but won't an opponent just not shoot the throwaway units and not trigger SfD?

In any case, you're gonna have a hard time triggering SfD on Reapers. I'd just rely on Yvraine to do that with psychic powers on one big unit. Take something that's a little more "in your face" for the natural SfD triggers.

Also, if you're worried about Alpha Strike, try a Wave Serpent for the Reapers.

You can get a Ynnari Battalion for 800. Example:

Yvraine
Warlock (pocket conceal for Reapers)

Dire Avengers, 2x6 + Exarch, 1x5 + Exarch

Dark Reapers, 1x8 + Exarch, all Reaper Launchers

Wave Serpent, Shuriken Cannons

If Battlescribe is right, that's 796 points. With just the core of Yvraine, Warlock, Dark Reapers, and Wave Serpent, you have 256 points ish to make 3 troops choices from.