geh, lost my whole post somehow... so I'll type it out nice and quick. Good list! I only have a few changes...
First of all, change your obsession to Flayed Skull. If your meta is cover heavy, it will make life a lot easier. When regular marines have a 2+ save in cover, they are difficult to get out. A blaster shooting would afford them no cover save, and a D. Cannon will give them a 6+... All your poison shots (44 in optimal range) will now reroll 1's, and take marines in cover to a 3+, which means you're inflicting double the unsaved wounds...
For your HQ slots, I'd take one guy with Famed Savagery and a Djin blade, take off the pistol. Wrecks face. The second guy, I'd switch the pistol for a Blaster, and give him PGL. Thats pretty much a wash as points are concerned....
This leaves you with 5 points....I think I'd use it to add another PGL to the Sybarite. You can add it to your other Archon as well. he has a higher chance of hitting, but you wont be able to shoot his pistol.... Personal choice really. I'd like em more spread out, since you can't really double PGL one target
Also, depending on the game/tournament rules/or what not, keep in mind that you can drop 1 command point to give your other archon the helm of spite if needed, against those psyker spam armies