No. It's not the main stat we want to fine tune. It's the substats that need stat selector for. Acquiring the main stat by farming is not that burning. If that Stat selector item is so rare, it will be a huge waste if you select the main stat, say Havoc DMG Bonus%, and you roll DEF, HP%, DEF%, HP as substats, this rare item goes to the thrash. It has no point. It's so far better to grind on your own earning the desired main stat, then use the stat selector to get the substats you want.