It's not like it's a minor/average ability that's being reworked, it's THE ability for demo locks. It's like If I went in to your favorite class, let's say, is a feral druid, and I said, "yknow, we are making a new class, that would benefit more from looking like a cat. So we are giving you the middle finger, taking a core mechanic of this EXISTING class, don't worry we will give you SOMETHING...I guess and giving it to the other class because some fanboys want to run around named Illidanx and circle jerk each other's glaives."
A death knight had much more room for reworking, they didn't have a core ability like meta that was given to a class years prior. It's what MAKES a DH, not the glaives, not the blindfolds, the meta. In fact, did you know the whole "ripping your eyes out to see through fel energies," is a VERY rare case among demon hunters? Even Illidan is unique for it, being his was done be frickin Sargeras himself.