Anyone loot arcane gear yet? Did you use luck?

[Ebereasider]

If ur initial drop is an arcane and u rerolled, it retains because Arcanes/heroics are of highest rarity.

If ur initial drop is legendary and above, reroll behaviour would roll a second time for a CHANCE for better loot. It either retains ur initial roll (if the reroll doesn't pull a higher rarity), otherwise it jumps to a higher rarity, and yes u can reroll upto arcane/heroic rarity if the lootable avails and if it can be affected by luck.

^
This is correct

If anyone still has doubt, here you go:

So if you get a mythic you can reroll and get arcane/heroic?

That's correct, though unlikely, since unless there's nothing less rare than mythic in the loot table, the second roll probably won't be better than the first, so it would stick with the first.

The way Mr. Futumsh says it means that it will just re-roll rarities from the same group. So basically a Mythic item can re-roll into Set or Vanity, but not Arcane or Heroic.

No, for the example of the first roll being a mythic, it rerolls from everything. If the second roll happens to be an arcane, you get an arcane. It's more likely that the second roll won't be better though, since the better rarity stuff is... more rare.