Why though Ocelot?
If Traya could develop such a technique, why shouldn't it speak for her ability and skill in the force? It is a move that "sucks" the force out of its victims. The masters that were killed were described as worse than dead.
Later she proved that she could use the technique out of the prescence of the Exile. She used it against all of Sion's dark Jedi, swatting them like flies in less than two seconds.
What do you mean develop Zephiel? Logically she got it as soon as she created a force bond with the exile while he was a wound. There's no evidence she had it before that. It doesn't speak for her ability and skill in the force because of the way she obtained it, she didn't conjure it up out of think air... And what makes you thnk she'll be able to use it on powerful force users?
Well the fact that she used it against three powerful masters SIMULTANEOUSLY, speaks for itself.
Lets look at the context. After the war led by Ulic Qel Droma and Exar Kun, the Jedi KNEW how to deal with Sith. They were prepared, there force powers were very offensive and militant, and the masters probably had more knowledge in the darkside than the PT council. Not to mention facing two subsequent wars by Mandalorians, a Sith War by Darth Revan and Darth Malak (who literally had academies dedicated to rearing the strongest Dark Jedi available) , and assassination teams sent by Sion and Nihilus, these three masters thought they were prepared for anything.
How do you even think that the technique requires the Exile at all? I mean it doesn't make sense. The proof even contradicts your hypothesis.
It is a move developed by Kreia, but inspired by the ancient Sith. Since Kyp has experience with neither, I doubt that he would be able to resist such a deadly technique.
What do you mean it contradicts my hypothesis? From my understanding she only got that technique after the incident on Malachor V, same time that Nihilus was created so no that doesn't contradict my hypothesis, it supports it. I don't doubt Kyp wouldn't be able to resist such a technique but I doubt Kreia could throw it at anyone anytime she wants. There is nothing to indicate Kreia would have that instakill if Malachor V didn't happen. Most likely she wouldn't have developed it and Nihilus wouldn't have come to be..
Of course she needed Malachor 5 to develop the technique!
But the fact that she was able to produce such a technique speaks of other abilities as well. It is an indication of her strength. She threw it around at whim when she destroyed the dark jedi.
The reason why she didn't start instant pwning everyone was
1) She was an advocate of manipulation and lies rather than pure brute force
2) She was still recovering from her seperation from the force ( credit to Sion and Nihilus here)
"While it is not yet explicitly clear which ending is canonical, the official stance from Lucasfilm on games where players can choose between the light side and dark side has traditionally been that the light side ending is the canonical one".
It is traditionally the lightside that is canon, and it said at the top that it actually wasen't decided. And this might not go for Academy either.