In my experience it's also always best to zero the characters pose before you apply another pose as well. And create a new group when 2 characters are involved and put them in it
You're correct that this doesn't hurt. The problem the OP was running into was that the pose itself included x,y,z positioning for the character, so when he applied the pose, it moved the character. I find this annoying, but in some cases it's intended to position a character at a particular position within a particular set. That I can forgive - when the poses come with the set. But when random poses include x,y,z settings, that's just laziness on the part of the creator, since they're not hard to exclude when you build the pose preset.
But your point about using groups is a good one - if you have a
pair of characters you're trying to pose, if you put both characters into a group, any "two character pose sets" that involve x,y,z will then do the x,y,z move with respect to the group, as opposed to with respect to your scene, and then you can position the pair within your scene by moving the group.