It's a bit disappointing that they didn't do anything to make Ynnari armies easier to take.
The stratagem they highlight in the article (United in Death) will never, ever be used. But yes, it would be cool if someone paid 589 points in special characters alone (and all 3 must be in separate detachments for it to work, so you've still likely got more HQs to pay for), and you've got a combat capable unit from each of Harlequin, Drukhari, and Craftworld all in combat at the same time, then pop this stratagem and look out!
It's a stratagem that you have to build an entire list around, the list will be worse than one not built around this stratagem, and even if you do pull it off, the result likely isn't game winning.
It's unuseably bad, unfortunately. Ynnari are still stuck being a single detachment for all intents and purposes. It seems like they really want people to bring the triumvirate, but there's no real incentive to do it. You have to bend over backwards to force them all in, and you end up with a bad list.