I have a 2011 EC250 that has pretty much the same "issue". I call it an "issue" because other than a slight inconvenience, I don't really consider it a problem. On my bike anyway, the clutch just drags a good bit with the engine off and cold. Once it's warmed up, it's significantly less, but I can still tell it's there. But once running, I can't tell it's dragging at all.
I think it's simply due to the surface tension effects of the oil. The plates are obviously separating as they're supposed to (else it'd drag with the engine on), and thus at lower speeds, the oil is kinda holding things stuck together until they get up some rpm. I've ridden the bike maybe 15 hours so far since I bought it, the clutch works completely perfectly otherwise (really well actually), and this tendency hasn't changed at all in that 15 hours.
Bottom line: on my bike anyway, I'm not concerned about it. It still starts easily both on the kicker and on the e-start with it in gear, so other than a very minor nuisance when trying to push the bike when it's off, cold, and in gear (which I rarely / never do), I'm not having any issues with it.
As for the oil, I recently had to put a rebuild kit in the master, so I obviously changed and bled the oil then. When I was doing some research, what I concluded was that when it says "mineral oil only", it basically means "any kind of oil other than brake fluid". Since some of the passages in the master and slave are pretty small, you'll want as low a viscosity as you can. I used some 3-weight synthetic shock oil that I had sitting around. As mentioned above, the clutch works and feels amazing. I'd venture to say the best feeling factory clutch of any bike I've ever ridden, and better than a lot of the aftermarket ones.
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