Let me begin by stating that I love DDO. It's a great game in many respects, and I've always loved how d&d tied together the various aspects of history, lore, and fantasy all under one roof. I also would like to state beforehand, that I know this issue has been brought up before (at least once) in a different form.
That being said, why is ninja a monk PrE? If we had to put it anywhere, shouldn't it be under the rogue class? From a Western perspective, I can understand the monk class is just "anything asian". Monks get to use all those other weps and have all those quasi-magical ki abilities, not to mention supernatural acrobatic abilities. But from an Eastern perspectives, it makes no sense to associate ninjas (sterotyped Japanese assassin) with monk (Buddhist/Daoist master of martial arts).
Ninjas were the original Japanese assassin. They are associated with secular organizations, poison, tricks, booby traps, stealth, dirty tricks, etc... Monks (as conceptualized in DDO) come in part from Japanese folklore with strong elements of Chinese martial arts. They are traditionally associated with monastaries/temples, meditation, healing, purity, truth, etc... There is also plenty of folklore to back up the idea of "evil monks" (those bent towards destruction or dominion).
I just don't understand how you can subcategorize these two elements. The closest analogy I can think of is creating a new PrE like artificer under the existing favored soul class, and maybe that's not bad enough because there are no/less cultural connotations. At the end of the day, this is just a game, but I think the inaccurate categorization of ninja under monk (rather than say rogue... or maybe fighter), has led to alot of gameplay problems, such as the synergy of shortswords w/ unarmed fighting; the relative "uselessness" of kamas, staves, and shurikens; or prevalence of monk/rogue multiclassed builds for "true ninja flavor".
I'm curious how people feel about this, and also, how many asians play this game. I will continue playing monks, ninjas, etc. in game because I love the concept. But I also feel that ninja spy is taking the place of a potentially much more apt and cool monk PrE (maybe Monk of Long Death? ionno, I don't play tabletop).