I only need Dirkee and Terror Spinner for Frostbitten, so I've parked an alt at one and set my hearth to the other, and log out at a spawn point.
It is, however, rather disconcerting to see someone else parked close to you when you log out... and in the exact same position when you log back in the next day. Do these people not sleep or work?!
Anyway, I've been trying harder to get this Achievement done because I was reminded recently that come MoP, zones will be cross-realm... meaning more people in the zone and therefore less chance of you seeing rare mobs. Great for questers, not so great for Achievement hunters like me! :(
Here's hoping I manage to get the Time-Lost Proto-Drake and the Camel Hoarder as well... although if the dude I see when I log into Storm Peaks is still there for the rest of the week, I'm not holding my breath!