I noticed that this item has a blue socket - however, I know that for arcane we tend to gem it with 160 mastery/160 hit; wouldnt it be better to gem it pure mastery (+320) and possible reforge out of crit into hit on another piece of gear? Or is it always better to gem partial hit instead (blue sockets) so that I can keep other secondaries up and avoid losing additional secondary stats, regardless of their weighting?
You can simulate it to answer yourself, but 160hit means you can reforge 160mastery from other pieces. crit is the worst stat but is not useless, so 60 crit is better than nothing.