Being a Fire Mage since the latest patch, one of my perks is Molten Armor earlier than normal.
Unfortunately, when I try to cast the spell, I get a "Target is too low level" error.
This can be reproduced by any sub-52(I think 52 is when you normally learn it) Fire Mage
Looks like Molten Armor didn't get it's use requirements lowered. You should be able to cast it at level 44 and above. We're looking into this. Thanks for the report.