I would look at this as: What are the demands of my event? and Am I training myself for those demands?
If one of these climbs is likely to take you 1.5hrs, then your goal should be to improve your steady 1.5hr power number. For me this would be long sweet spot intervals - work up to workouts like Wright Peak. FTP/kg is a great proxy for these long durations - make that go up.
Steady power is going to be key for those climbs. And as others have said, make sure you have the right gearing for the climb so that you can spin at close to your ideal cadence.