I would say try different rotation or just meld higher crit (i know you did not want to)
Honestly the VI materia is not overly hard to get, and you may get lucky enough one day running one of the level 70 dungeons and it will drop in your inventory

Your low crit is a big portion i think and also DH, which just for reference sakes mine is around 1900.
Some players favour Crit, others DH, personally i like DH but like to keep both DH and Crit fairly high