Did you just come back to the game or something and completely miss out on WAR's 2 years of unchecked prosperity and being guaranteed a raid slot?
If Defiance healed HP after switching to it, you would have to move Grit and ShO off the GCD to keep them balanced. And then players like you would still be salty.
WAR's new gap closer has considerably longer range than Plunge (20y over 15y) meaning that there is potential to aid in positioning and increasing your own uptime as well as your raid's uptime by keeping the boss static. DRK mains have been doing this for a while now. Optimal positioning directly translates to DPS and not just for you, but for the raid. Its also a knockback negation. So while yeah, it cuts into your FEEELLL CLEEEEV, there are situations where it'd be better to use it than simply lumbering back over to the boss while the boss runs to meet you in the middle, thus robbing your melee of uptime. You have to think of people other than yourself which I understand doesn't come naturally to a fair few of the more casual WAR mains.
Upheaval is literally Fracture with its potency consolidated into a single hit, and off the GCD, meaning that it is still going to be optimal in certain points in your rotation.
Inner Release I am certain is not one of the "useless" abilities you're referring to.
So that leaves Shake It Off as the only actually meme-worthy ability that is new to WAR in 4.0, and it remains to be seen if content will take advantage of it.
WAR never struggled with any content and they still have access to all the tools or equivalents thereof at the very least, that made them powerful. Its just that now, they don't have exclusive access to them, which means that you may actually have to compete with another tank for a raid slot down here on the dirty streets of the tank meta as opposed to living in an ivory bourgeoisie tower of being guaranteed a spot in any encounter you please.
WAR barely got nerfed at all, they just shared a bit of their wealth. They lost Bloodbath but gained Rampart, they lost Path but gained Reprisal, and while Defiance is a bit harder to just hop into willy-nilly, it penalizes you 5% less than it used to.