I think you had something melded differently between the two classes.

I had melds the exact same way, especially offhand tools, and was getting the exact same progress on those level 51 recipes, regardless of class.

BTW, it took me two CS2's to do those recipes at the start. Ing 2 did not help me at all. "Help me" being defined as reducing the number of CS2's needed to finish the synth. So what I did was use the following pattern :
CA, IQ, CS2, SH2, WN, HT, HT, HT, HT, Manip, SH2, WN, HT, HT, HT, HT, Byregot's finisher, CS2.

When I got to the point where one CS2 was enough to finish it (at exactly 169 progress) I dropped the first CS2 and swapped the first SH2, WN around to WN, SH2.