Retracking is usually the best option. If you are either stuck with what you have or stuck with struggling talent, well, then, make do.
If you are on a Mac, it's worth the $199 for Logic just for the Flex time (Elastic Audio equivalent) feature alone. It does a better job than Pro Tools Beat Detective/Elastic Audio for quantizing audio.
Export the audio and bring it back into Pro Tools and finish mixing.
See here:
http://www.youtube.com/watch?v=fgizL...eature=mh_lolz