If Haste and Mastery are my classes’ stat priority… why are items with stats like Vers and Crit being recommended? Is it really, hands down, better to mix the stats up instead of going all in on Haste and Mastery?
We need to see your specific case to comment.
In general, it is not always optimal to gear completely for two stats, even if they are the best two overall for your spec. All the secondary stats effectively multiply with each other, making their relative values shift with how much of each you have.