I've been testing a variant with 3 SoD replaced by a Protect Artifact, Mindgate and Purple Nymph.
PA didn't help me often, but if so it might make the difference. Mindgate isn't needed but speeds up the games a lot (though I had to destroy my Hourglasses more often). The Nymph wasn't really helpful (too late or too much control / healing until I got it and so didn't need it anymore - only helped me EM once IIRC), so I'll try changing it with a Purify.
I've also tried to replace all the 6 SoDs with Purifies to strenghen the "mass healing"-theme, but that didn't seem to improve the deck, on the contrary I had the feeling I lost more often.
@ the idea of dusk shield: I prefer Fog Shield atm as it can be played faster and often helps in early game - but of course replacing it with Improved Dusk sounds like it's worth a try