No, you don't. You're also lacking:
5% damage debuff (for 15 sec)
Can easily be picked up by AP and is not even stance dependent.
Ion Cylinder damage proc and movement debuff
The incredible damage of the Ion Cylinder procs I'd hardly call a tool to help defend allies. The snare effect somewhat, but AP has a guaranteed snare on one of their spammable attacks.
Damage mitigation via shields...doesn't affect much in PvP, but it does help
This falls under personal survivability, these are not tools to help defend your allies better. I concede that living a little bit longer means you can protect your allies longer, but only if you are not the last one alive.
Most likely reduced HP compared to a full spec tank
I must have missed that talent in the ST tree that provides it with a significant HP difference to AP?
I forgot about jet charge. Being able to quickly relocate to assist an ally is indeed a good tool.
Any derp can toss around taunts, so that's a wash. The only benefit you're gaining by switching cylinders is being able to use Guard.
It also adds survivability in the form of a flat damage reduction & an armour increase.
You'd benefit your team more by not doing it at all and just sticking with DPS. Stance/cylinder dancing isn't very productive for any class.
Who said anything about stance dancing? When I see its advantageous for me to guard a healer instead of providing extra dps, I'll use ion cell for a match. I love this flexibility in the tank classes. Making the best healer on your team twice as survivable can have an incredible effect on the outcome of a warzone, much more than providing 10-20% more dps. Not always of course, it depends on the situation.
Don't underestimate survivability. After a zerg by the opposing team, and the dust has settled, I'm always the last one standing. I can withstand focus fire from 3-4 attackers long enough for reinforcements to arrive. I often get "unbeatable" and even "immortal". With even a semi-competent healer at my back, you and your team might as well forget it. You're not going to kill me, ever.
To be fair, any tank class in its tank stance will usually die last, not because of incredible survivability but because the enemy team will focus on healers and then dps first. In addition, pretty much any class backed by a semi-competent healer is neigh-immortal.
While I'm in no way saying ST has less survivability than AP, the 30% damage reduction while stunned (usually when fighting alone vs 4 attackers they will inevitably chain-stun you) + a well timed Hydraulic Overrides means AP too can survive a fair amount of time vs 3-4 attackers to stall for reinforcements. Probably not as well as ST but I doubt the difference will be that big.