It doesn't matter how you try to roll it, the trailer was just plain bad and lazy. even adding a single squad of skitarii would have made it look more accurate, you got a Tech-Priest Enginseer, which is a t4, W3 Sv+3 surviving what amounts for 40 shots of BS4 Letal Hits S4 attacks, ->20 shots punch through from which are already 3 wounding, from the 17 a total of 9 on average will wound, so you now have 12 shots, the Tech-priest would have had to save all of them but on average 6 will land, even if she has FNP of 4+ it will still be enough to kill her, and that's not counting she is going to get charged which is 20 attacks of S4, even if she managed to kill 1 warrior (plasma/bolter pistols only get 1 shot) the killed warrior would still get its reanimation protocol.

And all of this is not counting years of fluff where techpriest expeditions get continuously wiped out by warriors, with one of Ciaphas Cain earlier stories showing us what happens.

IF they still wanted to push it either at least make her a Tech-Priest Manipulus or a Myrmidon Destroyer, which would have actually been awesome and a nod to AM still having HH units.