Gray Merchant is absolutely worth a spot. You don't need to drain that much for it to be good. If you start draining 6 the card is insane. Its also a simple card to draft around. I find less experienced players tend to go for the devotion decks (so they tend not to end up in the 3-0 category), but they really like having something they can focus on that makes sense and the card is a real deal reward.
I really like Sidsi, but if the game gets grindy decking yourself is an extremely real possibility.
Corpse dance and Demonic Pact don't strike me as build arounds, but just play them, they are awesome.
Hedron Crab is pretty good, but building around a dies to everything creature is heartbreak waiting to happen.
I hate Venser, blink is the worst.
Academy Rector seems mediocre. Maybe its fine. I love me some enchantment themes and I have plenty of sacrifice effects and any card that puts chromanticore into play is ok by me. I'll give it a go.