According to the audio technician I sent it off too, the issue he thinks is coming from inexperienced sound technicians in our city. He says, like Bryonsos suggested, "there is an issue with phasing from the original engineer; they seem out of phase with each other". So, it seems that by having sound techs who suck in my city, we're potentially getting a lot of wave cancellation/destruction with our audio.
But you said you actually DO hear the vocals clearly while you're at the shows, didn't you? Well, if vocals come up crystal clear while being there, but they turn out muddy in your recording, I think the reason is obviously a fault in your gear. If you've extensively used the M10 before without any noticeable problem, and you've also used the ST-9200 without fault... the problem might be in your CA-14's. The might be faulty or damaged in any way. Did you get them used or new?
Also, do you have the option of running two rigs (one with CA-14's and the other with CA-11's) at the same show with the same configuration (recorder, preamp, settings, mic placement)?? That'd be helpful. If vocals come up equally muffled, it's the venue/engineers fault... But if vocals come up clearer/much clearer on the CA-11's... You know.
Just a newbie's $0'02 though.