I discovered how devastating a combination involving Saboteur + Synergist and Rav/Rav/Rav (to Stagger) can be, followed by Com/Com/Com if applicable, for absurd physical damage if your target doesn't block that kind of thing. A combination involving one or more Medics is of course not a bad idea to keep around. I actually ended up using Vanille rather a lot - she's a fine Ravager, but a quite handy Saboteur/Medic even so. Snow or Sazh I'm not very familiar with. I suppose Snow is the quintessential Sentinel - maybe a general purpose combination along the lines of Sentinel/Commando/Ravager, with Vanille as a Medic for Those Ugly Turns?