Dunno what u guys are doing? Could it be that both of u are doing 110 instance instead of 105?
I do 105 instance on 107 archer and get c grade. My gear is bloody r99 bow+8, Elmore cloak+7, octa warrior ring, blessed aq, atlas earing +12, the rest are twilight paulina jewels, dex+15 dyes, artifact set lvl2 (all artifacts +0), dex head gear, LVL 3 brooch jewels, longing talisman, venir LVL 9, kaliel bracelet+3, veterans mask+4, dragon shirt+2,exalted set, exalted seed bracelet, cancer agathion +3, some +5/+10 skills (most are still not enchanted all). I use dc buffs and all the free pots from daylies. I use single target skills.