I had a much harder time healing on my shaman than I had with my druid.
I think it is a tuning issue, but still, I managed to heal Shadowmoon Burial Grounds, so maybe you need to change something about your healing as well.
Unleash Flame has a 20 sec duration, Unleash Wind has 30 sec, and Unleashed Fury has 8 sec. I hope that answers your question, because I'm not sure which 12 secs you are talking about :/
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And for the Elementals out there: Do you remember the Spell effect form our old lightning/magma mastery? The Lightning effect was added to Fulmination!