To be honest, after the 10.2 patch, the damage Death Knights are totally useless. In 10.0 and 10.1, Unholy was effective in raids, but without external buffs, it was just mediocre. In the Mythic Dungeon International (MDI), it performed well, but since most players don’t participate in MDI, you cannot optimize your game for the top 1% of the top 1%.
Now, with the new 10.2 patch, we’ve lost relevance in raids. We are no longer a priority target for Power Infusion (PI) and other externals, and without them, Unholy is weak. I personally welcome the new direction of shifting Unholy from burst to sustained damage, but now we are stuck between a rock and a hard place. We don’t have the burst for externals, and we still lack damage outside the burst window.
In Mythic+ scenarios, Frost with Breath of Sindragosa is not compatible (a pug won’t chain pull for you), and Unholy just doesn’t deal enough damage. It lacks a good mix of AoE and single-target damage; you can only excel in one, either AoE or single target. The AoE is strong when there are more than 8 mobs, which is not frequent in pug Mythic+, and with Mythic+ talents, it lacks any single-target damage.
It’s not an answer to the DK’s uselessness to say, “wait for the legendary weapon” because we are playing now, and the current state is terrible. Nothing is guaranteed to be the best scaling from the legendary (after all, if a Warrior or Retribution Paladin scales better, they will take our spots if they become strong enough).
For a class without strong Mythic+ mechanics (you can have your own cr with engineering), it has to deal a lot of damage to be relevant. At this point, Unholy/Frost is just as weak. Even if they receive a 20% all damage aura buff, they will still be useless.
You can check the world-first runs; there are no DKs. You can also check Raider io; there are no DKs in 20+ keys.
What I want is either a stronger Mythic+ kit or a better and stronger damage pattern,
in Raid just need more sustained damage or a bigger burst.