I'm so glad I got to use this combo because Neymar Jr is free. A missile rack and an assault weapon on guardian with Neymar Jr is killer. First of all, mobility  enhancer and guardian is already a match made in heaven. A burst damage missile weapon and a comparatively high dps sustained damage weapon is yet another match made in heaven. Combine it with high energy capacity and it hurts every which way. The huge burst damage on a splash weapon can control crowds of enemies and the sustained damage from the assault weapons can pressure enemies by safely doing damage from behind cover as your missile rack reloads. It doesn't always get the most kills, but it controls the battle. You have to try it.