Thank you for the suggestions! I had thought doubling it might not feel mythic enough within the context of the book.
I might go with something like spending a mythic point to make it function as deathwatch for 1--or maybe 10--minute(s). That would be a cool benefit but not so strong as a constant deathwatch!
Don't underestimate the usefulness of being able to notice living foes from twice as far away. XD As a third option, you could also expand it to let them detect undead entities (and discern whether they're living or undead), since undead are fairly common foes and all.
Expending a Mythic Point for Deathwatch is probably not a good choice. A smart Oracle probably took Inspired Spell in the first place (you're using the FAQ for that, right?), which already gives them access to Deathwatch for 1 MP even if they don't know the spell, and it would be a bit redundant if their Lifesense power did the same thing.
Oh that's a great point, haha. I was wrapped up in the mythic class abilities and completely spaced the path features... and we do indeed use the errata.
I quite like the undead detection, as they have a prominent role where our (homebrew setting) game is taking place.
Thanks again for your suggestions!