What deletes valkyrie?

So, I like to brag about advertise the immortal

Valkyrie. At lvl 50 she gets ~8k hp after CtA, 85 all res, crap ton of armor, plus ~50%

Evade chance and regens >5% of life per second
Essentially unkillable, and normally facetanks whole t5

Herald packs

But sometimes, she just gets deleted..

1) lvl 49 valk vs bloody porcupines in act 1, t5

Herald pack. I think they were cursed and with

Fanaticism. Deleted her in <1s. They then hit my bowazon pretty hard, but she survived at her ~2.2k hp and mawed them down. What was it with the

Valkyrie?
2) lvl 43 vs ghosts in

Tal Rasha tomb in act 2, also t5

Herald. she runs into them and disappears. lightning zon the deletes the ghosts with a few pokes of her Infinity without taking any dmg. what was it?
3) against uber ancients I think i know what it is, but maybe someone can confirm. Her res is 2 per lvl, capped at 85. So say at lvl 50 she has 100 res, unaffected by hell penalty. then the

Conviction kicks in and brings her res to 0 or even negative. then 1-2 elemental shots and she's in valhalla. right?
Also some site says she can get immunity if her gear rolls with res on top of her natural 85 res

Cap.. is it true? then she would be kinda survivable even against the ubers (but you never know until you meet them..)

Database description for

Valkyrie by

Stormlash says "Sometimes Valkyries may have Immunities on higher difficulty. You may wish to recast

Valkyrie until you get one."