Finally got my lumina today. Haven't had time to play with it but the collector in me is glad to finally have the stupid thing, from what I seen it synergizes really well with mid tree solar warlocks which is pretty cool.
Sadly the damage buff doesn't stack with well but shooting a fireteam member with a Noble Round does trigger Benevolent Dawn just like a charged healing grenade so if used well, your grenade, rift and melee abilities are always up. Lots of healing.