Well, the ritual being a means of controlling the beasts has much more sense in regards to the rest of the plot than a totally unexplained and later forgotten attempt to resurrect or take advantage of a dead Sith Lord in which nobody had any interest whatsoever.
And when they say that you are too late, they may be referring to the beast bringing down the forcefield, and therefore, the ritual not being necessary any longer. It doesn't really matter if you can kill the poor thing in two strikes, it's supposed to be a really tough beast. But as we all know, the game is broken when it comes to gameplay mechanics.