We're lacking in two areas right now and while not an easy fix, I don;t think we're far away from being a consistently top side.
1) Genuine all-rounder: someone who is a threat with bat and ball on a regular basis. It's not Neesham, it's not Anderson. If we had a player in the AR spot that can offer us 2-3 key wickets and 25 - 35 runs each time, we'd take a big step forward.
2) Spin: there is no NZ spinner up to Test Crciekt at the moment and no spinner in NZ would make any other test side or even the A side for that country. The exception MAY be Patel who is taking bag of wickets for fun in County Cricket. Bearing in mind his home pitch is a bunsen burner but at the very least he has a ton of overs udner his belt and maybe Hesson should be giving him a few calls.
Though I think Anderson is the better of the two, in both departments.