The strength accessory will hit their limit at lv 11 if I remember right. So once that happens you can transform them. Being on Gran Pulse you should have enough to upgrade some into Warrior or Warrior beyond which I think is Scarilite (spelling), though I wouldn't spend too many. Just know that Warrior goes from 100 to 180 at cap and then next one Power Glove goes from 200 to 250. So you can get a pretty good boost from that.

With your current party doing Medic x2 and Sentinel should be a good healing paradigm for you and all you'll need. Lightning should have Cura and Cure that will help while Sazh just uses Cure.