As far as voting him worst newcomer, I think the emphasis comes from injury concerns and "unknown" value without Nash as compared to his contract, most of which is guaranteed.
I think that Amar'e can score without depending on the pick and roll. But, he will get his opportunities with Felton running the point. Felton can average 8.5-10 apg with this lineup, and Amar'e will benefit as well. But, Amar'e will almost have a mismatch and will get plenty of isolation opportunities. Obviously, I disagree with the worst newcomer bit.
I think Amar'e, without his injury concerns, is a better player than Bosh.