In 359ilvl gear, 3556 Haste, 13.4% hit, 10k itterations.
Looks like I'm round about a Haste plateau here, which going by this spreadsheet would be for Shadowflame. Looks like Haste improves again while I get more, while Crit and Mastery trail with roughly equal values.
Those things might change once I'm hit capped however. A lesson as to why to sim your own gear, rather than rely on figures posted for gear you don't yet have.