I like Warrior and Dark Knight and I have cleared just about all content with both of them throughout the life of the game. Where they are right now though, I am still not happy with how Delirium feels (although it's still in a better spot than any previous iteration of delirium). I also feel like both of them could use some procs or something else to juggle during moments of downtime, and with the way that healers are being proposed to change, Living Dead needs another pass to be in a better spot. I do like Fray but timing him exactly is difficult with other raid buffs because he doesn't activate his first ability for the first 3ish seconds of the CD duration.
Honestly the thing I miss the most switching from WAR to DRK is the readily available charge with Onslaught. If you are using the other tanks' gap closers effectively, you typically are wasting them back to back during openers or cooldown periods. With WAR, it has a REALLY low cooldown and is only ever down during IR.