It's totally personal and even dependent on the bike. I run a 39/50 something on my race bike with a 12-28 on the back and that works fine for me on that bike, but I'd never run gears that big on say a touring bike. OTOH I think I run bigger ones on my TT bike, which I wouldn't ever use for a super hilly race. My rain bike has the same gearing as my race bike, but runs smaller wheels. While theoretically it has "easier" gearing, it's heavier (especially the wheel set) and certainly doesn't climb as easily as the light bike. Every bike, every rider an individual.

I'd say start with a larger cog in the back. It won't be super expensive to test out a 12- 28 or 29 (I think you can get that configuration...) If that's still not enough consider switching the shifter back or going for a compact. Depending on the Bolt pattern on your crank, you may be able to simply swap your 39 with a 34. I did that with a triple once - went from a 30-42-52 to a 39-52 with the small ring locked out.