I don't know anything about placement or anything like that.
i think
this is probably a good start.
I agree with you about the reverb. I knew the vocals needed something to make them fuller.
<trade secret>
use two delays for the lead vox, panned hard L and R. for the delay amount, they should have a 2:1 ratio (no hard rule on which is which). initially, try shooting for one at a quarter note, the other at an eighth, but this can vary based on the song style.
set the feedback so you get several repeats on each, but i like to vary the number (one may have 3 repeats, the other 5, for example. again, doesn't matter which is which).
with the lead vox and delays solo'ed, bring down the level of the delays such that you can still hear them, but not so much that they sound like obvious delays. we're talking subtle here.
now bring in the rest of the mix. what you should hear is the lead vox having a different sense of space -- its own -- but not the delays themselves. the delays are something you should
sense, not hear.
after that, you can send just a bit of the (non-delayed) lead vox to the reverb buss, to help it sit in the soundstage. it should be a good deal less than you "needed" before.
</trade secret>
an example of this technique can be heard
here.