Not necessarily, such a war would've brought in France and probably Great Britain and possibly even the United States. I don't know whether this would've been better or worse than a quick defeat by Germany.
France, certainly, but The British Empire and America? The former MAYBE, if somebody tries for a "rally round the Flag" tactic to handle the domestic powder keg set off by the Plot Against Ulster , Royal Assent Crisis, and Dublin riots long enough to stop radicals on both sides from escalating things into the Civil War, as serdog mentioned. But isolationist America? What about a war mainly in the boonies of Eastern Europe over the assassination of a monarch's heir could possibly attract them of all nations, particularly with things still as chaotic as they were in Mexico? I mean, such a war would certainly not be better for those counteries, particularly France, but it'd no doubt be better for Russia in the medium term.
Still, The Third Balkan War's biggest impact was always on (surprise) the Balkans, and the biggest winner of the series of wars after only 3, as opposed to 7,would no doubt be the local Balkan Orthodox nations. The sheer economic exhaustion, infastructural destruction, debt accumulation/inflation, and casualties suffered by Bulgaria, Serbia, Montenegro, Greece, and Romania from those oppritunistic spats and the "circular firing squad" of backstabbing the weaked rival/winner of the last war went a long way towards the resurgence of the Ottomans and their Albanian clients in the region, to say nothing of the ethnic stress lifted off the Hapsburgs as the more troublesome Romanian and Serb nationalists migrated to the economic oppritunities in the region in a mockery of American carpet bagging.