In reality, the CAP metagame is shifted toward balance and stall, rather than offense. So adding another tank would balance the metagame in a way.
I disagree with tennis on this one. The addition of Pokemon such as Revenankh and Pyroak being able to come in against DPPt monsters like Heatran, Scizor and Zapdos already make it a much more balanced metagame than standard OU. Stall is more viable here than in Platinum OU that recommends offense.
The addition of yet another tank or wall meant to take on these threats will mean much unless we create a pure counter. A physical Blissey is completely unecessary in the CAP OU metagame because outside of Earthquake and Close Combat, which both do very little to Revenankh and give Pyroak enough to survive, the metagame is run by Special Attacks.
These Pokemon - Heatran, Scizor, Shaymin-S, Zapdos, for a few examples - are still going to be dominating the offensive metagame. Another physical tank will just be a thorn in their side. We aren't creating a healthy and diverse metagame by doing so.
It's all a chain - when something new is added, the metagame shifts to accept and adapt to that addition. A brief example of this is how Scizor's acquisition of Bullet Punch led to an increase of Heatran because it was a good counter. That led to more Suicune and Vaporeon, which in turn led to more Zapdos. Zapdos itself was a great counter for Scizor with Heat Wave, etc.
An example of this on the CAP server was the introduction of Stratagem. With a Rock Special Sweeper on the loose, Tyranitar, Hariyama and Machamp have been increasing as far as I can tell. Tyranitar's acqusition of Aqua Tail in Platinum has also led to a decrease of Hippowdon.
Adding a Physical Blissey will not diversify or set off a "chain reaction" in the CAP OU metagame because the metagame is not in need of it. Scizor and Tyranitar are the only major physical CAP threats, and they are kept in check.
