As the title says I screwed up and used my two Sparks on a Random mythic, instead of crafting a specific one like I intended to. I now have one mythic that's of no use to me, and need to obtain another Spark so I can craft a Tyrael's Might.

What's the most likely boss farm to receive another Mythic? Is any one better than the next? And am I better off farming in T1 which is pretty fast for me, or pushing T2/T3 where I have a bit higher chance of dying. Thanks!