Then the battery life will be horrendous. The dual core wont make up for that much in efficiency, not enough to negate the inefficient LTE modem.
Incorrect. See the Bionic for an idea of how much dual core can improve battery life, coupled with good power management software. The LTE modem was only part of the problem; the other was an inefficient CPU and poor power management programming on the part of HTC. They've had over 6 months to figure out what went wrong with the Thunderbolt, and remedy it. I had the Thunderbolt and I've had the BIonic; I can tell you right now that HTC did a half-assed job with the modem software in the Thunderbolt.
That, and we have no idea yet if it even HAS the MDM9600.
Why does HTC do this, use first generation parts in what should be a second generation device?
You need to get your head straight when it comes to the bolded part. HTC has no control over this. Verizon HAS NOT approved any second generation LTE modems yet, so it would not be possible for HTC to put one in the Vigor. This isn't a second-generation device by any stretch of the imagination. Like the Bionic, it is a bridge between the first generation single core devices, and the true second generation devices that have multi-mode chipsets.
It is the price of riding Verizon's initial LTE wave; you have to get used to not having the ideal solution for connectivity until well after the network has finished its initial rollout.
They should've waited for Krait.
And wait until January? Do you think Verizon and HTC are stupid?