Agreed -- once you've stacked two 1x2 plates... might as well just treat them as a single part from then on. With two pairs of pliers of the correct shape, you might be able to get them apart.
A 1x1 in the middle of a large plate though can be a challenge though. While the remover tool works for e.g. 1x2s, 1x1s don't quite have enough surface area, so the tool often slips off.
2x plates I find tend not to give as much trouble, if only because they require more force to have been pushed together perfectly flush in the first place.
(My context is teaching Lego professionally to middle-school children for a few summers. You get given all sorts of fun things to take apart, and having a pocket knife around isn't a good idea. My other takeaway from that experience is that the LabView-based Mindstorms software is/was total shit.)
Beside using a knife, the only trick I've found to work for these is to stack longer 1x plates on either side of the pair, which give you more leverage on the center pair, while themselves being easier to take apart.
This: