I think it's fairly obvious that monsters are spread to accommodate the least experienced players who struggle to fulfill their role. There has been a shift to pull more monsters because the playerbase has figured that there is a better/faster way to complete the dungeon, who push themselves and excel in their individual roles. This means everyone uses their CDs effectively to both live through large pulls as they are being killed quickly with AoE damage.
If certain players are not as well-accustomed to their roles and the rest of party would like to finish the dungeon quickly, it is completely fine to dismiss an underperforming member in favor of one who is able to play through regular dungeon content. This is a playstyle difference and dismissing someone under this pretense is completely legitimate.
Everyone is free to play their own style, but remember, you're in a party of other people, majority rules. Please stop villainizing superior play.