well I think...
at 2nd base there's cano....and then pedroia and kinsler who are both only drafted in the second round because after them there are no more 2nd baseman....
at third there are all of these players who basically outperform the rest of 2B...
your premise is wrong about 2B (and some of the guys you threw in for 3B are dubious, at best: alvarez? middlebrooks? moustakas? even zimmerman)
Tier 1: Cano
Tier 2: Zobrist (especially in OBP leagues), Kinsler and Pedroia
Tier 3: Altuve, Phillips, Kipnis, Hill, Utley and Prado (and I think Weeks has a bounce back year)
All of those guys are projected higher than Middlebrooks, Moustakas and Alvarez at the moment. Some are projected higher than Zimmerman, too.
I'll stick by my theory that 3B isn't as deep as 2B. We can agree to disagree.