It holds the job back because it's the only mechanic keeping the job together. Because TBN is so powerful, it would be busted if something like Oblation had the effects of the other tank CDs. A big reason why we don't get big, more powerful skills is because of how good TBN is and I really don't see a future with this skill alone unless they do some god like expanding on it. Then again, wouldn't it just be easier to make the other 3 job resources mean something? Rather than putting all the effort into one skill alone. Basically, they can't keep riding on TBN alone without at least expanding upon it in an interesting way.
This isn't to say I don't like TBN though. I love counter attack moves and if things like Shield Swipe procs could be gained from putting Intervention on someone else, that would be great tank design. Actually rewarding you for defending. People tend to forget that we're tanks and don't really want to be scuffed DPS.
