From a power point of view the 4 USB ports on the Microsoft DOCK Station draw: 1 x 900 + 3 x 500 = 2400 ma
Could they have gone: 2 x 900 + 1 X 500= 2300 ma?
If that is the case,then perhaps the adapter in question needed to be supplemented with an external power supply to work to full spec: which is not an elegant solution.
A while back I bought a 4-port Targus USB 3.0 hub. The hub is fairly small but connecting to the SP2 requires using a beefy USB 3.0 cable, not nearly as elegant as the plug-in-the-side solution.
OTOH, 4 ports are better than 2. I haven't checked the port speeds, or the power drain. Notably the hub does come with an external power supply--use is optional, and for portability reasons I almost never have plugged it in.
However, I've used the hub quite frequently (powered by the SP2). Haven't noticed a remarkable difference in battery life, but then again, small decreases are hard to measure in light of all the factors affecting battery performance. Wouldn't be surprised if there was--everything has a cost.