i'm one of those people who's into rare combos, but mainly only if i can be the "first" to have that combo. i like the challenge of making a combo that no one ever wanted into something pretty, and i like the satisfaction of seeing my dragon show up first when i search for that combo.

there are actually lots of combos for which there are less than, say, 15 dragons, so, paradoxically, merely being a "rare combo" isn't that rare. a dragon would have to at least be the first unexalted dragon of its combo for me to be interested, personally.