During prerelease, all Stormwind cards are uncraftable and non-dustable. But on another thread, VBrainstone pointed out that Celestalon tweeted about this, and the answer is yes.
You can’t get regular Prestor, but you could open a golden Prestor in pre-release. (And you wouldn’t open her after the reward track unlocks, unless you had every legendary already.) There was the same issue with Mankrik, you might open a golden Mankrik in prerelease then a regular one from the rewards track – so they let you dust the golden one.