I had a DK (tank) as my main since launch day of WOTLK until legion launch. This expansion, I switched to demon hunter. The main reason that I switched was that mobility on death knight felt terrible, and demon hunter felt like the exact opposite.
Recently, I have started leveling my DK and am considering making him my main again. Mostly I'm back on my DK because the fantasy and lore around being a DK feel badass to me.
One thing that has struck me, is how the class fantasy fits with mobility. The lack of mobility given to DK has been attributed to DK being sort of a slow, unstoppable force. I used to understand this fantasy somewhat as a DK tank, but I really don't anymore. In doing leveling dungeons, I have really been struck by not having icebound fortitude and lichborne. Not for the damage reduction or self heal potential, but to be able to break stuns and fears. I'm really missing those CC breaks that made me feel like that unstoppable death knight that keeps powering forward no matter what you throw at him. At least there is still AMS that you can time to avoid some mechanics.
Just wanted to rant that my DK doesn't feel like it used to. Wondering if anyone is feeling the same about mobility and class fantasy.
I'm going to keep giving my DK a shot, hopefully these things will bother me less as I adjust to the class changes.