Can arenas end in a draw?

Apparently they can. Blizzard poster Nethaera had this to say about draws:

When you play a match and it ends in a draw, it does not count as a match played. No one will be scored with a win and no one will be scored with a loss. Your ranking will not change.

And what constitutes a draw?

I don't know how close it judges it. It sounds like people who have had a draw knew full well it was a draw as soon as it happened since they both died at the same time. Best bet is to win handily to avoid draws. ;)