Im a little confused as to what... the great kahns are. I know they're nomadic tribals... but are they raiders? and if they are raiders... they seem a little.. less brutal than your average raider. they seem to be more interested in stealing supplies, rather than killing.

I give you the history of http://fallout.wikia.com/wiki/Khans

so.. it still leaves alot of questions open.. like did they still enslave people when the raided NCR towns/outposts just prior to NV?

They are on the far civilized end of Raiders. Like the Brotherhood they harm their environment because of laziness to grow their own crops instead of pure evilness/kicks like the more usual small time Raiders. Khans are quite vile sometimes but they often show very understandable traits and nobility. They are the so-called http://tvtropes.org/pmwiki/pmwiki.php/Main/NobleSavage. The Khans let anyone join them if they just pass the ritual, treat their people fair and are ready to cooperate with others if it serves the common good - raiding caravans seems more like just poking the bear rather than active campaigning.

That said they were your typical heartless Raiders in Fallout 1, but by NV they have become a more permanent faction, one with members eager to start a new more balanced life.