I'm just looking for a survey of opinion. If Abrahamic religions had generally failed to spread beyond Semitic-speaking peoples, is it likely that the Dharmic territory would have expanded much more widely? Or is this an unwarranted assumption?
I find it very unlikely that Buddhism could compete with Hinduism in Persia, while the Dharmic religions had no real ground in the Roman Empire even in the third century -- and I think, in the absence of Christianity, the Mediterranean would have met some sort of pagan synthesis (not unlike in China) that could probably compete with the Dharmic religions.
Certainly the Dharmic religions have the best chances at winning converts among the steppe peoples, but I don't see any strong reasons for a Dharmic Mediterranean or a Dharmic Iranshahr with a no-Jesus POD.
Greaco-Buddhism was a thing, and I imagine that if no Christianity it could move westward and become part of the religious synthesis in Europe.