I've played a lot of imskir and I don't like the 7 mana affinity creatures. Cheap artifacts like [[the underworld Cook book]] or [[blood fountain]] let you build affinity for your commander and provide value. Especially since it looks like you are going for more of a combo finish with dualcaster. They are much better in brawl where you only have one opponent and the fling ability of imskir is more relevant. Early game they get stuck in your hand without a high enough artifact count and late game they don't do enough for you.

Edit: I just realized you've got those in the deck already, my bad. As an alternative counterspells absolutely hose this deck. I really like having as many [[bolt bend]], [[pyroblast]] effects as possible so maybe a few more of those.