I have never played a monk, but i did spend alot time with my barb before rerolling to my wiz.

I generally think monk has better utility as in teleporting and constant interrupt on mobs not to mention serenity. While barb is a more in your face kinda tank which requires alot more gear to take hits. In the end i've ditched sword & board and went 2handed to clear act3.

Bottom line will need to look at the amount of ehp require to clear both a3 and a4 with both classes.