In reality, putting pure DE against Ynnari is an uphill battle from the start. We're considered to be one of the lower tier armies, and pitting them against a conglomeration of all of the cheesy Eldar units seems doomed to fail.
Personally, against Ynnari, I think that running pure Covens will be our best shot. Grots and Pain engines give us high toughness multi-wound models that'll at least deny them some Soulbursting. But whether or not that's worth sacrificing the higher mobility of our army is arguable.
"Death solves all problems. No man, no problem."