As others have said, one initial scatter plus 3, then 4, then 4 again if you go for the max. And it is -glorious-. I'm not just talking about hordes. With just two of them you can saturate 3+; in my sims, it's been especially nasty against deep striking Tau battlesuits. If you're throwing huge numbers of 4+ rending wounds, even if they've got a 3+ each time, you -will- get through, especially if you position your later hit flips (all they have to do is intersect, so you can get a lot of mileage out of that). And it is very, very pretty on danger close if you have a Primaris Psyker on divination-- he casts Misfortune on your target, and oh, look, RENDING. In a "sit back and shoot" theory build I've made, I double-
CAD'd, with each having a 2-Wyvern squad and a basilisk, plus two primaris psykers. (the downside is that I can't move much; the upside is I can do
heavy denial, especially with the odd bonus shots from my heavy weapons &
MoO, drunken basilisk that he is.
Another thing to note is that if for some reason something survives your barrage under that beautiful stormshard rain, if it's within 36" and
LOS, you can lay down fire with your heavy bolter as well-- there are benefits to not being ordinance.
The downside to squadding them is that you -are- restricted to a tight area. If your opponent isn't deepstriking, or is podding, etc. and they have any wits about them, they're going to spread out. For a large enough horde, you can be swamped because you can only scythe out one area at a time (and it is a red harvest on Vassal, oh yes). Honestly, as much as to get the second Aegis Line as to be able to separate out both the lisks and double wyvern is why I took the second
CAD.
Cough.
Anyway, basically, as soon as you hit, and Twin-Linked gives you a righteous chance of doing so, you can think of an area of anything with Marine Equiv (T4,
Sv 3+) stats as going bye-bye most of the time. The Wyvern is a powerhouse. That being said, it's also a big fracking target and like its older brother Basilisk and high-note-hitting older sister Hydra, it's on a chimera chassis so the sides are really, really vulnerable-- if the aforesaid deepstrikers bring enough firepower to the game, they can potentially pop the squadron, which is why Camo Netting, Divination Pyskers with Fore...er... warning, I think-- yeah, forewarning.
Re: Nosferatu1001, I believe that all subsequent flips come not from your additional flip, as per:
Once the first marker is placed, roll a scatter dice for each other Barrage weapon shot fired by the unit. If an arrow is rolled, place the marker in the direction indicated so that it is next to and touching the edge of the first marker placed (see diagram below).
(I hope that's an acceptable quotation; I'm pretty sure it qualifies under Fair Use?)
For hits, I haven't had the luck of having a Wyvern on a tabletop, but my plan is to put ye olde generic markers from my L5R
CCG games, once per hit per model, and keep track of flips on a
D8 or
D12 (I'm presuming a single Wyvern shouldn't be too hard).
You know, rereading, I think it's even more boss than I thought. It looks like you tally hits and wound at the END of the sequence of barrages, so if you're shooting, say, 4 marker drones, 3 plasmasuits, and Farsight, and they're tightpacked from Deepstrike, you can manage 8 chances at a shredding wound per hit rolled. I'd been simming it as though the number of potential hits goes down with each kill, but looking at this, I don't think that's the case.