As far as mobility goes, it mostly comes down to how people perceive it's ability to negate knockback effects. As such, giving tanks parity with either mobility OR knockback mitigation would suffice. As it stands currently, both WAR and DRK have mobility while PLD has an isolated knockback immunity skill, so it works out well (Aside from maybe the CD of Tempered Will being 180s which seems rather long for such a niche skill)
Then as far as mitigation and aggro goes, WAR's are the bottom of the totem pole in terms of mitigation, so if Tank Stances were a thing, it would be relevant that other Tanks have more tools for mitigation, while WAR would continue to rely on either outside support (I.e. PLD for Intervention/Cover) or immunities to deal with TB's reliably. Then for aggro management, they're actually pretty close to being the best constant aggro generation. Given that their Enmity combo is merely 10 Beast Gauge away from being their best DPS combo. Butcher's Block combo is higher potency than Storm's Path, but Storm's Path gives 20 Beast Gauge instead of the 10 that Butcher's Block/Storm's Eye gives.
Literally drop the bonus Beast Gauge from SP or bump up the generation of BB and they'd be spamming their Enmity combo all day and thus be kings of sustained enmity.
On the topic of TBN, I feel it's able to be put on allies in order to give some level of OT presence. Given that MT's still mostly use DPS stance and DPS combo's, the only thing that really differentiates the 2 roles is when the OT can provide support to the MT in some way. Especially when DPS between tanks are so similar that the decision for OT comes down to who provides the most utility (Which invariable ends up with PLD > All). Hopefully with their 5.0 designs where they mentioned about possibly making all 4 tanks able to perform well in both roles they'll look to address this in more thematic ways (I.e. It would make more sense for DRK to debuff damage with Reprisal to aid the MT)
As far as WAR's not getting some obvious utility skills like Raid DPS buffs, likely it comes down to how everyone and their cat has been yelling about how OP WAR is and how they have too much stuff for like 6 years. Not to mention, that a Raid DPS buff would just further push WAR into the meta which pretty much defined by "What composition does the most DPS".
To be honest, I'd love to get Bloodbath back. I'd happily trade Raw Intuition for Bloodbath again. I could even see Shake It Off being replaced by something akin to an AoE Bloodbath that works on magical damage too (Focusing more on their "Tough out the damage and come back swinging" design as opposed to slapping an AoE shield onto their kit). To be honest, I'd also love to see Mercy Stroke and Fracture come back. Possibly in the form of Beast Gauge spenders, so that BG isn't just about "Spam Fell Cleave" (Or if Tank Stance becomes relevant "Spam Inner Beast") - Especially if Inner Release was re-done to not be infinite BG skill usage and was something more interesting (Especially if it also incorporated making Crit and Direct Hit stats relevant in some way given that it already provides their effects at 100% chance for the duration)...