I like that list a lot. I'm not sold on the Grav weaponry on Sternguard since they have the poisoned shot with their Bolters, but you have enough Melta in the RAS that I think you might have it covered. I would drop the Power Swords in the DC for an extra Combi-Grav in the Sternguard, as well as a Lightning Claw and Melta Bombs for the Priest if I were to run it, just a personal preference I guess. This is assuming the Priest has a Jump Pack, since you haven't included it in your list. Otherwise drop the Swords in the DC for a Claw and Pack for him.
I don't have time to run the points here, but if you wanted to include Sanguinary Guard what if you ran something like this where you dropped the Dreadnought (who would have been First Blood bait if you didn't go first anyway) and ran two HQs and a LOW?
Dante
Libby - ML2 (Wings of Sanguinius would be great for Sternguard to have!)
Priest - JP, LC/PS (whatever you have)
10x DC (packs, PF)
5x Sanguinary Guard (PF)
Podded Furioso (Frag + Heavy Flamer)
Podded 9x Sternguard (3x Combi-Grav)
5x Tac. (Lascannon)
5x Tac. (Lascannon)
Podded 5x RAS (2x Melta, combi-melta)
Podded 5x RAS (2x Melta, combi-melta)
Podded 5x RAS (2x Melta, combi-melta)
SR (AC/MM)