If it was current content, like an EW boss FATE, I'd say to leave it as it is. But for older content? These boss FATEs shouldn't require so many players. Considering the effort necessary to pop some of them and then have a small chance to actually clear it? Keep in mind that the kind of players that will do these boss FATEs are NOT there for seals or experience. There are better places to earn those. They are only there for the achievement.
Someone that pops this FATE needs players that likely meet these requirements:
- don't have the achievement
- care about the achievement
- have nothing else better to do
I can't tell you how many times I've seen a boss FATE fail simply due to lack of interest.