a thousand threads, what metering are you using? evaluative/partial/spot or centre weighted average? for that sort of situation I would use spot metering and meter for the midtones on the persons face. a couple of those shots it looks like you really nailed them, but the others looks like you metering picked different places for the reading so I'm assuming you used evaluative. also depends on what effect you are trying to achieve, if you want a good strong silohuette then meter for the highlights in the environment. also open your aperture up. what camera/lenses are you using?
this one of yours is really great
this one of mine i used spot metering and metered on her nose, it took awhile to get the metering and the shot as she was spinning around quite fast. patience is the biggest virtue but it is also very difficult to take lots of time if someone is paying you for the shots. i was really quite lucky with this shot too as i was trying to mix the band that was playing as well for an audience of 1100 people... fun times. from memory this was iso3200 at about 125th of a sec.
