Who needs Markerlights when you're going to simply erase any vehicle you shoot at unless it's a Land Raider or a Monolith?
Less flippantly, I like it; you don't need
many Markerlights when you have Coordinated Firepower - even 3 or 4 is getting towards excessive unless you have a lot of units Gone to Ground or snap-shooting.
Is it better to use marker drones by themselves maybe with support from a buff commander (if it still exists haven't read the new book yet) or yet again pathfinders.
Buffmander still exists, but you're much better off putting him in a squad that's going to fire after
you shoot Markerlights; while he's nice as a tank character in front of Drones, giving potentially every unit in your entire army Twin-Linked, Ignores Cover, Tank Hunter and Monster Hunter on top of whatever Markerlight benefits you got (and probably a huge stack of them, since you dump every Markerlight in your army on your Coordinated Firepower target) is too good to pass up.