Our Rift Knights are extremely nerfed in the early stages of the mid game when Talent 30 speed at level 10 is stripped. This talent is extremely important for DK as it gives this hero the ability to deal stronger damage relative to the midgame, providing the perfect push for the house with his Green Dragon form.
Talented replacement Breath Fire's ability to reduce damage is not enough to replace it and this makes DK from a regular hero first pick at both the pub and the league down to only one hero has about 52% winrate, very low compared to 55% before 7.10.