Picking a lv90 emp (or any set of emp armor, for that matter) for your prize is a huge squandering of the odds you just defied to win it, there's pretty much no way around that. This can be easily determined by simply comparing experiences between people who've finished any sort of empyrean stuff (a whole hell of a lot of people) and people who've finished things like a relic or mythic (a whole lot less, particularly so for mythic). I can and have finished whole sets of +2 armor from scratch for people in the span of a single day on several occasions, no joke.
As much as it's perfectly within one's rights to choose that as their prize, it's also perfectly within my rights to laugh at them for it :s