The Armenians helped the Russians by keeping Ottoman soldiers from the front

Source: Justin McCarthy, Death and Exile: The Ethnic Cleansing of Ottoman Muslims, 1821-1922, The Darwin Press, 2nd Printing, 1996, pp. 192-193:

There is no documentary evidence that Russian authorities orchestrated the initial Armenian attacks. There was no need for them to do so and the Armenians could be safely trusted to disrupt Ottoman territories on their own. The Russians, however, did all they could to facilitate the Armenian uprising, including seizing the weapons of Muslims in occupied territories and distributing them to local Armenians. Those with the most to benefit from Armenian actions against the Ottomans were the Russians. The activities of Armenian units and armed Armenian villagers allowed the Russians to free men who might have been needed in Anatolia and the Caucasus and to send them to the Russian western front.

Regarding normal military actions, the Anatolian Armenian units were most valuable behind the Ottoman lines, cutting telegraph lines and engaging in other "commando" attacks. They also served as advance units of the Russian army in its 1916 campaign. The Armenians, however, were far more valuable to the Russians by keeping Ottoman soldiers from the front. This was particularly true in regions such as Van, Zeytun, and Musa Daǧi, where major insurrections kept thousands of Ottoman soldiers occupied. With eastern Anatolia in a state of insurrection, the Ottomans were forced to keep many soldiers far behind the lines to protect the population. These soldiers were thus removed from the battles with the Russians. The Russians thus not only gained Armenian fighters for their side, but kept Ottoman soldiers from the front - a valuable pair of assets [69].

[69] Herbert Gibbons, admittedly a very pro-Armenian source, contended that the Armenian actions in Eastern Anatolia had resulted in the diversion of  "five Turkish divisions and 30,000 or more Turkish and Kurdish irregulars" from the war to put down the Armenian rebellion. This may be a gross exaggeration. Armen Garo asserted that the Armenian revolts in Anatolia, particularly the revolt and occupation of Van, saved the Russians from defeat by the Ottomans (Why Armenia Should Be Free, p. 22)