I use duos reasonably frequently to get the specialist/toolbox + gun "voltron" unit blob shoved upfield. If 3-model links lost +1 burst, I probably would've kept using them in N3, but probably not in N4. There seems to be more of a focus on jack-of-all-trade profiles in N4 like the Kosmosoldat SO, Evader AP Spitfire, whatever that PanO HRL + FO thing is called, etc, so there isn't much of a need to "voltron" more capabilities into a blob that moves up the field. I'd still use a duo though, mostly to drag an expendable bodyguard sort of profile around to have some ablative wounds for something like the Evader. 4- and 5-model links are just like playing the game with oven mitts. It feels clumsy, unfocused, and a bit of a hot mess. I didn't like them in N3, and I still don't like them in N4. I'll use 'em if I have to though... sometimes you gotta do what you gotta do.