I'm not gonna lie, I think Kara is at best mediocre at singing live. I saw a couple of their MR Removed perfs, and they weren't pretty. I saw the girls during Dream Concert too and they lipsynched in either Lupin or We're With You. It's nothing personal, but it's one of the flaws of Kpop in general I think. The girls have solid voice, particularly Ham, Gyuri, and Nicole, and it's nice whenever you listen to them actually singing but it's clear that they are untrained to sing and dance at the same time.
Dance wise, I agree with the majority that Nicole is shakin it. Hara is a close second. I also think Jiyoung is holding her own, but she has a limitation because people will totally scrutinize her if she dances too sexy. Gyuri and Seungyeon is okay I guess.