> Indra is also god of sacred verse, "vipratamo kavinam", which is similar to odin mastering the runes

That seems pretty tenuous; at the time Indo-Iranian diverged from the European branch, runes didn't exist at all, and most likely the proto-Indo-Europeans had no writing of any variety.

For example, different families' words for writing:

- write [English], from PIE *wrey;

- scribere [Latin], from PIE *(s)kreybʰ;

- graphein [Greek], from PIE *gerbʰ; (cognate with English carve)

- likhati [Sanskrit], from PIE *reyk(ʷ)h₂;

- neveshtan [Persian], from PIE *peyḱ (cognate with English paint)

[all taken from wiktionary]

This doesn't look like a concept that was around before the groups diverged.

I know that that Vedics didn't have writing. But the runes and Vedic "brahman" (sacred verse) serve the similar magico-religious function. Odin is also associated with poetry.