You may try combining that fury shower with disruptor shots, which are slightly more effective against shields. However, if you want my advice, that energy is better spent in your engines in that dogfight. Also, an Apollo carries many more furies than a Valk, so I recommend you fly one. Lastly, if the Scorpions are too slippy for you to shoot them down, maybe you can try destroying one of the Shaitan bombers instead.
On easier difficulties it's quite possible to "save" the Plato, though it will ultimately self-destruct when you kill enough Shivans.
(Anecdotical side-note: Once I harassed one of those Shaitans for so long that he actually fired a bomb at me. Kind of funny.)