At this point, I have leveled 9 classes and tried every spec on theses. Obviously some of my characters are less geared than others and I didn't played them that much, but it's not really the case of my DK that has been one of my main alts for the first tier progress, sitting at 378 ilvl right now.
Plus, I used to main DK in legion so I did every progress on this class as DPS playing the best spec each tiers so UH during EN, then Frost MG, BoS during NH, UH for ToS and back to Frost oblit during Antorus.
There has been some highs and lows in term of gameplay enjoyment, but overall DK has been a great class to play during Legion. On top of that Blood was a true blast to play during Legion due to everything being off the GCD, we were able to setup huge pulls extremely quickly while having a very dynamic and nervous gameplay.
Now, I didn't wanted to play DK for BFA just because of how bad the class played during the BETA. And holy shit it might be my best decision for a long time because the state of the dominating spec is just atrociously bad, I have never played an iteration of Frost as bad as the BFA one.
It's complete garbage from the first talent row to the last, the rotation is slow and boring like it's never been with huge downtimes, the GCD changes makes it even worst and is very noticeable. BoS uptimes wich are suposed to be the high moments are NOTING like NH Nervous and intensive ones.
So yeah, from all the specs I played Frost is definetely the worst one with Arcane mage, much worst than BM hunters btw.
Part of that are the shit feeback that the DK Discord gave during BETA(wich is leaded by a few people giving their opinion wich is suposed to matters more than all the players on the discord btw), I will never forget thoses people saying that GCD changes "are not that bad" and PoF almost removal would not be a great because it was such a boring spell in the first place.
Now we have this,a shit gameplay spec that only keep existing because Blizzard is giving great numbers to it.