Hi,
In the scenario you describe, then yes vPC object tracking would help, but you're now trying to consider multiple simultaneous failures and design to accommodate. You need to consider the likelihood and risk of such failures. This is always difficult and sometimes the design / configuration to mitigate those scenarios imposes a greater risk than the dual failure scenarios you're trying to consider and protect against.
For example, suppose we've now configured vPC object tracking to cover the scenario you highlight. But now we have a different dual failure, that being a failure of module 7 in N7K-1 and module 8 in N7k-2. You'd still lose the vPC peer link, but now both Nexus 7000 would identically decrement their tracked priorities, and the object tracking would have no effect. In this case I assume the "status quo" would prevail and the operational secondary would disable its vPC member ports, and so result in an outage.
If there's an obvious dual failure you can easily protect against, then I believe it worth doing so. Equally I think it an almost impossible task to consider and design against every dual failure scenario and becomes a case of diminishing returns.
Regards
