I went 25 DEX and 5 VIT. I have very little threat issues up to Garuda. Was rocking the Barbarians Bardiche for the longest time, no materia, and only recently put in some STR into my ring. Had some issues with relic and +1, but for the most part threat has always been solid. Perhaps your rotation is not as optimal in regards to building and maintaining threat. Not saying it is or isn't. Just that I rarely have issues. Something worth looking into possibly. It could also be my lucky 777 mp?