The Prussian foreign policy - dating back to the Napoleonic wars and the Congress of Vienna - had more or less constantly being based on the Russian support against the Austrians. It had worked reasonably well, with the only exception of the Erfurt crisis which ended up with Prussia being humiliated at Olmutz, and it had become even more important once Bismarck got the chancellorship: the Prussian support to Russia at the time of the Polish insurrection of 1863 had been appreciated very much (Russia had become quite isolated in Europe after the repression) and the reinsurance treaty had been equally important for Prussia in 1866 (and - in minor measure - in 1870 too).
The League of the Three Emperors was a logical follow up, but the Europe of the last quarter of the 19th century was not the post-Vienna one, and the conflicting appetites in the Balkans would unavoidably pin Austrian interests against the Russian ones. Bismarck might have taken a middle way, in a sense, by keeping the alliance with Austria and at the same time renewing the reinsurance treaty with Russia: the problem however was with the big Prussian estates which were mainly producing wheat, and were resenting the cheap imports from Russia. The choice not to renew was "forced" by internal politics rather than diplomacy, but this does not make it the right one.
A-H did not bring any additional strength to the alliance (nor the expansion of the alliance to Italy produced any benefit), and its ambitions in the Balkans were not supported by an adequate strength. As a matter of fact, the weaker and more trouble A-H became, the more they felt pushed toward military adventures.
Damning Russia as a "disunited and oppressive" state might be acceptable, but not when compared with A-H: both of them were "disunited and oppressive".