On the vocoder, a couple of things, as I am learning it as well. This one comes with Ableton, but I am sure they all operate the same. I am using a (external synth, comes in from another track) sound with a fast attack and I use a note at the start of the each word. Then hold the note for as long as the word, next word new note.
That mid-freq. you're talking about is what I have been trying to control (there is a type of freq EQ that you control what freq pass through), I heard the same thing and tried to tame it and still get a the sound I was looking for. I thought I had it under control (I didn't sound bad to me cause I had heard it so many times when it was worse), but I know what you are talking about. Real annoying after a pass or two.
I tried pulling down the stab, work on that a bit more, couple of ways I can do that, the velocity, I hit the keyboard pretty hard, so it is high, or try turning it down on that channel. I will see if I can get those things dialed in a little better.
Thanks for the feedback.