I personally feel there is no need to rush crystal keeper G since it's pretty tough and you really need more than just 2 AW archers for that map. also, nagi is the only potential ranged melee that we should get within the next couple of months, but even then having saki is good because nagi and saki fulfill slightly different roles (saki more for wave clear and nagi more for slightly armored units). and that's assuming you don't get fucked over by not having a ranged melee during the events up till nagi's event.