I was looking at the tool tip of inferno and its morphs, and I noticed that the morphs both list a 15% magic reduction. The base form does not list this, and after some testing I noticed that there is no reduction on either morph. I assume this is a change from a previous build, but the tool tip was not changed.
I noticed this as well and have avoided morphing it to avoid the magicka hit. It's good to hear that the reduction doesn't actually happen, but I really hope it stays that way. That said, I'm not sure I like what they did to the skill in the first place...
Short answer is DKs likely won't be seeing a ton of changes before we go live; this class is still quite powerful (as it should be being a tank), even after some of the adjustments we've made to other classes and abilities.