Thought of another idea to give Demon Hunter an exciting play style.
Make Metamorphosis a form that you build towards. Eg. every 50 fury spent grants a charge of surging fel (max 10 stacks). After 6 stacks, you can consume the fel to deal some damage and enter Metamorphosis for 1.5 seconds per stack consumed.
You could make is more complicated by having surging fel connected to an ability like fel blade, which would give some procs to the spec.
Just thought it would be something to make the play style slightly more engaging and offer some choice rather than hit everything on CD.