The Battle of Tannenberg was a disaster for the Russians, but the contemporaneous Battle of Galicia against the Austrians had been a resounding success for Russian Arms. It's going to need a more substantial butterfly than Nicholas II developing cold feet to end the war on the Eastern Front in 1914.
Fine. How about the French losing at the Marne and the Germans putting away the war early?
Its possible.
Though a much better scenario would be the US intervening in 1915 and tipping the balance towards the Allies before the Russian Revolution could have taken place. There certainly was ample justification after the Lusitania (sp?) and other similar incidents to do so.
Or a more aggressive campaign against Austria in 1916, knocking them out of the war.
And finally, if Nicholas had caved in and allowed the moderate Tsarists in the Duma to have a greater impact, some of the disastrous appointments that Nicholas made like Sturmer, and Protopopov would not have been made and better decision made with regards to supply and organization. Though even more competetant regimes like Kaiser Wihelm's couldn't survive.
Then there are the scenarios going back and changing more of history like Alexander III living and leading the country in WWI. He was only, I think 50, when he died in 1894. Rasputin never would have gotten anywhere close to being in a position of influence as Alexander would have either executed or exiled him. However 1905 would have taken the real bloody route and Russia would have still been a completely absolute monarchy. And not the pseudo-parliamentary in name only monarchy that it was.
Then the final one is Alexander II not being killed in 1881 but dieing in say 1885 or 1890 providing him the opportunity to create a Duma much earlier and giving it time to get up and running effectively.
I wish I could develop on yours our one of mine more. Maybe this weekend I will see what I can do.