I had farmed the Eye of Sulfruas on my druid for about 4years, nothing, not one drop, then i got both halves of Thunderfury in one run randomly, so, even though i couldn't use it i made it up lol, (Sucked i didn't get the achiev though, even though it got my guild the achiev o.O) Then i got both halves again, which sit in my bank, then i finaly got the Eye of sulfuras after getting it twice on my warrior while trying to get the TF halves lol, and since then I've seen it drop 4more times, (i Still run MC because i love it
)
Basically keep trying, i had no luck for years then within 6months saw 12 drops in MC of legendarys>.<