We 5 manned story mode (8m) and we 9 manned SM (16m), so I totally agree with Infalliable Tionese/Columi is fine for story mode.
HM I would also agree at least for the Tank to be BH or better, however for dps, depending on tanks and healers skill/gear, Rakata or better is fine for dps. Of course like Infalliable wrote, it will all depend on the skill/team make up. We’ve done it with 2 healers and 3 tanks and the rest dps, so numbers of dps made up for any shortcomings in dps gear. It also helped that we had two scoundrel healers, as we could ignore some game mechanics and just stealth rez a tank or a dps that accidently taunted. However, we were largely pretty well coordinated as the majority of the group has been playing together for over a year, some since launch, and we were using Vent. In my opinion HM 8 and 16m is a joke too, but I know that feeling comes from my group and my opinion would be vastly different without those people if I were just pugging it. Although the one group I pugged with last time, made HM 16m Xeno seem like a joke too, but I just healed with a guild that needed a healer, so other than me they were well corrdinated.