I'm ok with this but it feels like a lot of effort will be wasted for their humanoid form as you'll never be able to see this. Also, I find it kind of lazy, or even lame to design classes around transformations on which you can't see your character.
Always been an issue to me that druid and DH spend most of their active time in animal / demon form than in humanoid and that blizzard never designed anything to allow them to fight in normal mode (a glyph to make demonform just make the DH be bigger, maybe a primalist form for druid who just make them mimic their animal attacks ...)