Please excuse my incoming wall of text but I haven't found any definitive answers on the internets yet so I figured I'd try here.. So, I've gotten my warlock to level 8 and am on the 2nd tier of skills and I noticed I haven't unlocked any new skills in a while so does anyone know how the progression system in destiny works? I read somewhere it was speculated that doing the action in that tree would unlock it (I.e. to unlock the whole grenade tree use grenades) but when I have my first tier grenade mod equipped it doesn't seem like the 3rd tier progress goes up until I've equipped the 2nd and I'm still on the 1still tier nova bomb skill. Does anyone have a link to info on this topic, would be greatly appreciated :-)