So what about...
Well...now we know his answer. Of course many will vehemently disagree(I don't. I agree completely and that's the way we've been playing it).
But this begs the question: What if you take your partial action _first_ and do a 5' step as part of that, and then you want to move as part of your normal action?
In other words, is it legal to do the following(while hasted):
5' step(that avoids an AoO)
Cast a 1 action spell.
Move you're full speed(30' for an unarmored human)
Cast another spell(or single attack or whatever).
I say no. Once you do a 5' step to avoid an AoO, you can't move further for the rest of the round, hasted or no. You've moved in such a way that you are concentrating on maintaining your defense, so you can either continue to move in that manner or you may stop after only 5' and act "normally" for the rest of your round, but not both.
Another option might be that you can move your normal move minus 5'? I don't know, though because that makes it so you can weasel out of AoOs and still take two actions and move your full speed. I don't like that.