It doesn't auto-crit, it does around 1400 dmg on a hit at 111. Its purely for the extra shard gen (generates 2 shards)
No relation to destro talent at the moment, I'd honestly be surprised if the destro talent sticks around. It really serves no purpose in destruction's kit, it just saves you 1 shard every 45 seconds and does a little more damage than a chaosbolt. With demo getting soulfire again (and talents to go with it) it'd be strange to leave it in destro's kit.