I thought you weren't partisan but that wasn't a very good effort.
The excise tax on (the excess benefit of) high cost plans is designed to get insurance companies to lower the rates (and perhaps some of the frills) of the better plans and to get employers/consumers to buy cheaper plans that they actually need instead of just giving insurance companies extra money en masse (might as well give it to the government where it will be better utilized in that case) as they have been for decades.
Even with this tax looming five years in the distance, 17% of companies have opted for cheaper plans already: "According to the International Foundation of Employee Benefit Plans 17 percent of employers have revised their plans as a result of the tax this year. Thats up from 11 percent in 2011."
The excise tax wasn't devised merely to soak the middle class, as you say, (with the family limit of $27,500 this probably doesn't effect most of the middle class), but to change their habits (and those who don't change after over 7 years of warning will help pay a bit more dearly for America's healthcare). Another reason for the slow implementation of this is because group plans are bought well (years) in advance so companies/unions need time to revise their plans/contracts with employees. This is a large factor in why nearly all of the healthcare system overhaul is proceeding so slowly.
Lastly, the whole concept of "insurance" being a "benefit" of working is meant to be disappeared. Regardless of whether or not you get a federal or fortune 500 company job, one should have "good insurance." When taxes on individuals were high in the 50's employers got in the habit of providing "benefits" (company cars, lodging, better insurance) in lieu of cash to avoid that direct taxation, a habit that's never been unlearned despite plummeting individual tax rates (well for the upper classes, or in your book, the middle class).
It makes perfect sense for the government to close such "loopholes" if it loses substantial revenue to those loopholes and even more sense if consumers are unwittingly throwing away the money they earn in the process. The government is giving people/organizations time to adapt to that alteration and guiding them to make themselves richer instead of making insurance companies richer. I see that as good.