I think you mean the ATMega168 and its power consumption is somewhat less than 0.0027W, while the BCM2835 is more like 2.5W, but regardless, I think you're defining overkill in terms of power, which is only one dimension, probably not the one the comment was referring to.
It's a bit like saying using a tungsten lamp is massive overkill in lighting a room.
A BCM2835 (Raspberry) uses ~2W, while an ATmega186 (Arduino Duemilanove) uses ~0.027W. So yes, massive overkill.