Also, it would appear that you cannot apply the 10.10.2 combo updater to 10.10.1, only 10.10.
Correct. That means that this Combo update differs form all previous ones in that it isn’t applicable to all previous subversions (even if there are only 2 in this particular case). And that's decidedly not good, as many Yosemite users have found out. With the next update we'll see if this is the shape of things to come or just a one-off. Let's hope for the latter.
