Short answer, pick Defense Multipler & Attack+15 for every Ranger.
Not to discourage you from playing the way you want, but even my fully emblemed Gill-Ra, Gunnar, Balthazar and Rudolph have trouble surviving in the last levels of their class quests.
Click to see pictures of them fully emblemed
Keep in mind these are maxed and fully emblemed 3* heroes having trouble in the last level of class quests – they are useful while they’re alive but they can’t take much abuse before clocking out.
So I don’t imagine it’s any better with a 1* hero.
Now if you still want to go with a 1* on a class quest, then I’d say for Rangers the most important thing is attack – their tree and talent naturally fits that route. I doubt defensive boosts will help out Sharan much anyways, so attack all the way is what I’d do.