If you count Zoroastrianism as a Dharmic religion then this is actually pretty easy with the right POD.
Zoroastrianism is not a dharmic religion. The dharmic religions have in common the ideas of samsara (life, death, and rebirth cycle), karma (the concept of why there is that cycle), dharma (the cosmic principle behind the cycle), moksha (the release from that cycle) and forms of yoga (the ways by which one can achieve moksha).
Zoroastrianism has none of this. Zoroastrianism is much closer to Western monotheism in its principles with a creator god, a second power behind evil, prophets of the god, etc.
I think the easiest way to accomplish the POD is if there was a more successful proselytizing as a result of Asoka sending out Buddhist missionaries. Conceivably, the maritime regions of the Arabian penninsula (Oman and Yemen) could convert as a result of trade with India, and eventually that would spread up towards the Hedjaz. That would butterfly away Mohammed and Islam and possibly lead to the Arabs adopting some kind of dharmic religion, perhaps by syncretizing Buddhism with native beliefs like how the Tibetans did.