So, it's been a while (3xGTC) since we've had a draft format that was as aggro as this one (this is not as fast as Gatecrash, I don't think).

In KTK and to some extent DTK (with or without Fate) you could be reasonably OK with starting on 3, although having a couple things to do on 2 was alway nice.

Putting aside dedicated control or super aggro decks (ie. multiple non-bonded construct 1 drops) - how many 2 drops are you comfortable running in your basic midrange deck. 4 seems to be the minimum, but I would count Reave Soul and Bonded Construct. I guess Elvish Visionary counts, although it doesn't really block much. Fiery Impulse?

I would count Disperse into this category. In fact, Disperse and Fiery Impulse are usually much better than bears. I would play a lot of Bonded Constructs, but it's not easy to get them. They block just fine, and are very easy on your mana.

This format has the tools to punish aggro decks that go all in with auras and combat tricks, namely bounce and, again, auras. You should plan to always have a play on turn two. I'm fine with four two-drop creatures, and will play as many cheap tricks/removal as possible.