The short answer - it doesn't really hurt the Sith. It gave rise to the most powerful Sith Lords of history towards the end of the line. There are no strategies that actually work, since the Sith will never have complete domination of the galaxy.
For the long answer - if we track the records of all the other Sith Empires and measure their success, then we can tell that, by far, the Rule of Two was the most successful Sith doctrine and the Order of the Sith Lords was the most successful Sith Order.
Vitiate's Empire never gained full control of the galaxy, and they only won the Great Galactic War because they had several free surprise attacks, and the Republic never won a victory until ten years later. The Empire hardly even won in the end (the Empire was also badly damaged), and they didn't manage to obtain full or near-full control of the galaxy. The Republic remained an opposing organization for the following decades, and presumably Vitiate's Empire was vanquished at some stage. And this is all despite over a thousand years of rebuilding and planning, and the fact that Vitiate never had to show his face in public.
The New Sith Wars were a thousand years of battling and they all died except for Bane. The Old Sith Wars were equally unfortunate for the Sith. Exar Kun lost Ulic Qel-Droma, and then he was beaten back to Yavin IV where his spirit was trapped. The Jedi Civil War was also not a success. Revan ended up being betrayed, then redeemed, and then he destroyed his own Empire. The fragments came together to form the Sith Triumvirate, only for its head (Traya) to be betrayed. She then raised a pupil to finish off the Triumvirate. If you come back to the Great Hyperspace War, the Sith failed once again because they were betrayed.
Krayt also didn't have much more success. He managed to establish himself as Emperor, but with even more resistance than Palpatine had to deal with coming up even more quickly, it was hard for him to rule and he never even managed to properly establish galactic-dominion or near-galactic dominion. He was quickly assassinated later by Cade, and his Empire was something that he planned for about a century.
Palpatine didn't need to plan for a century. He just continued the tradition set down by Bane, until he became the most powerful figure of the dark side, then he terminated both his master and the Rule of Two at once, took over the galaxy, and became the Emperor for about 23 years. Sure, it didn't last forever, since the Sith aren't intended to rule the galaxy forever as they plan. But Palpatine's Galactic Empire is the most successful Sith-driven empire in history, beyond Vitiate's or Krayt's. Some people like to argue that the Rakatan Empire was better but I recall some sourcebook claiming that the Galactic Empire was the greatest.
In any case, it is still the most successful Sith-driven empire, since the Rakatans aren't Sith. Empires filled with other Sith will eventually fall to each other because of individual Sith's greed and ambition. Vitiate's empire was endlessly filled with backstabbers, traitors and conspirators. As soon as Vitiate faded from public image, there were Sith that immediately tried to become the Head of the Empire or start a new Empire.
Palpatine's Empire might not have been filled with Sith, but it was filled with immense numbers of mindlessly loyal troops. Treachery was slightly more limited, but the most important thing is that it was almost never a real threat to the Emperor, simply because the traitor just isn't powerful enough. The only other Sith in the Empire was Vader, who could never threaten Palpatine after he was maimed on Mustafar. That's why he was successful - apart from the fact that he was only one who tore down the Republic to minimize resistance.
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