Remember that with 40% off, the more expensive the room, the more you save. 40% off concierge at the Poly is "worth" a lot more than 40% off a standard value. The value of free dining is less subjective, and is a flat rate depending on the size of your party and the length of your stay. It's hard to say what's the best "deal" for each family, but it seems the "cheapest way to go" is staying at a value on free dining...or maybe staying at a moderate on 40% off and not eating!
I've learned that you need either an advanced math degree or a really nice CM to get the best bang for your buck at WDW!
ETA: I always start by pricing everything out at rack rate, separately and as a package, and then as each "deal" comes out, I price that out and see what I save. HTH!