You're really correct about low quality/vague posts. This has been discussed here many times.
It's really annoying when the post has limited or poor info, you apply and then find out that the job isn't what you thought. I've been in those shoes on many occasions.
Maybe a solution would be to ask the client a series of questions and clarify their requirements first, and then someone with great writing skills can take charge of writing the posts rather than the client themselves.
The quality would then be consistent. There are plenty of quality writers/freelancers on this site, so they could even do it.
I am totally agree with you. Last month using 60 connect got only 3 jobs and they all ware very bad experience in my freelancer career. The new buyer wanted me work like a slave paid only $60 total and 1 buyer wend away not giving a penny and now my Job Success 83% from 100%. I am totally frustrated. Hope odesk will have a look on these things otherwise it will be really impossible for us to keep our existence.