I saw this on your blog a while ago and the reasoning behind this list is very sound at least.
I'm not a
DH player though, so my critique will be of limited use, but at the very least I want to see this list get some more views! I think it's a really nice idea and I love your use of unconventional lists.
I think I'd try to max out Veterans with Meltaguns if possible, as you said yourself you're lacking on melta. I'd at the very least swap the single Plasma Gun for a melta.
I think they Grey Knights at the core of this army are good. I'd see about squeezing the extra-armour on the 2nd
LR, but otherwise I'd just advise tweaking around with various Guard set-ups within the rest of the list to see if you can find something a bit better?
I'd also wonder about squeezing some Mystics in, but that could be difficult to do and remain the internal balance of the list. I'm sure you're aware of the likely hood of lots of deepstriking armies being at adepticon too.
Looks cool though, I'd love to see how you do. It's not going to be easy going, that's for sure!