Also I might be wrong, but doesn't the shielding ability also have the effect of removing force ghosts? Or was that a one time thing?
It should be possible, but the ritual can't be used during a fight. The consular would have to win first and then shield the inquisitor.
I Imagine it assassin versus sage, so I would put it the inquisitor would win. Lightning is stronger then telekinetic powers. The inquisitor would shatter any projected rocks at him, to the point where the consular could only defend against the lightning and saber attacks, unable to even attack. Finally, his resolve will fail, and the inquisitor will dramatically kick the consular into a pit, saying In his Creapy and British voice:
"Watch your step Jedi."
Well, when you block lightning with your saber, it doesn't hit you. When you block a rock with your saber... you're hit by two rocks. And an assassin cannot be lightning specced, so his lightning wouldn't be that strong.
I can see the assassin winning, but not through "lightning". The assassin wins either by hitting the Sage by surprise (Deception specced), or by taking a defensive position and waiting until the Sage makes a mistake (Darkness specced). Zannah for example did the latter in many fights.
(I know I'm mixing story with game mechanics, but because of the vastly different fighting styles this is necessary.)