Firstly, given the three formations combine to a valid Lion's Blade, so the entire army can be made to fire Overwatch at full ballistic skill (when not jinking).

I presume you mean an Auspex on the Chaplain, not a Signum.

If you go with the drop pods, lose the jump packs on the assault squad and give them one too - odd numbers of drop pods increase the number that automatically come in on the first turn (since you round up).

I would suggest Gravguns on the Ravenwing - you've got enough plasma elsewhere, bikes make good use of salvo and if you went with melta instead you end up being too close for comfort after popping the vehicle.

I ordered spare bits online to swap the arms on two of my DV terminators to TH/SS, totally doable conversion.

I'm not convinced by the multimeltas on the dev squad - they're short ranged weapons on non-relentless bodies, I can't see them being a viable threat. Lascannons would increase the likelyhood of damage from the get-go, and wouldn't need a transport. If you stick with the melta, take drop pods and hope they survive long enough to get a decent shot off.