WAR was in a really bad place in 2.0 and it was only in 2.1 that it took off. Imo WAR retained a lot of these old quirks because it was a job designed with a specific theme in mind and every expansion it has expanded on that while staying nearly consistent to its previous iterations. No other tank has retained its core design for more than 2 expansions yet WAR has literally never changed, outside of how much self healing it gets.
Also, vengeance is so miniscule now that removing it will only further homogenize the tank role. It honestly doesn't even play a factor anymore since most savage bosses auto with magic and NF no longer is affected by it, meaning it can't even heal from the counter damage anymore. Removing it will only piss off WAR players similar to how over power was changed. A change so redundant when you consider that WAR has access to other circle aoes like SC, Decimate, Orogeny and Primal Rend.
WAR is just there to prove that having a consistent design around what the job and expanding on it's current tool kit can make the job better (BLM is also in this category). DRK is the anthesis to it, having changed every expansion in pursuit of some random idea or being top dps. Dark Arts was conceptually sound it just needed to be worked out and not affect offensive ogcds to avoid double weaving (yet ironically that happens more now). If DA only affected combo gcds and maybe one or two defensive cds it would have worked. SB was the last time DRK matched WAR in terms of utility, damage and tankiness.
DA could have been the polar opposite to WAR's Infuriate. Both acting as their respective jobs "identity" and their tool kits revolving around it. WAR's Infuriate and later IR are iconic but DRK lost DA (which was an amazing animation). The only thing DRK has retained is that it has the most options when it comes to aoes, having access to line, ground, target and circle. Probably the only thing consistent about the job's tool kit. Rather than trying to remove WAR's skills maybe they should focus on making the other jobs have quirks like this.