For the love of the twelve, yes. Or at least read a guide about what you're boosting. Both the ASTs I had in my Zurvan normal just now were level boosted. They let the MT die somehow which made Zurvan turn his sights on my squishy BLM self. Thankfully Lucid Dreaming and Diversion saved me. I ended up dying though to unavoidable damage from the DoT he throws on you to break the seals because they threw zero heals on me despite me being right next to one of them.

Pretty much my experience with boosted players has been terrible. However, I don't think it's even because of the boost because I'm sure they'd still be terrible otherwise. I'm just getting them in my groups in later content because of it.