I wholeheartedly agree that Dressage is the most important aspect to focus on. Dressage here in North America is the most competative stage in Eventing, and when you get into Novice and higher here, you are facing tough foe's and if you don't do well in Dressage, you are struggling the rest of the HT to climb the placing ladder and are relying on your competators to fault or get refusals or time penalties or even Eliminations to get up to where you want to be - and that isn't how it should be.
If GP horses can do minimally level 3 dressage, and if Jumping is Dressage with Speed Bumps - there should be no difference in your training - which is dressage being the strongest.
I learnt so much when I was in PC and I can thank my years of riding in the organization for the majority of my experience and knowledge. Heck, I am an adult now and I still apply what I obtained from my years back in PC to this day.
With how many accidents that have been occuring in the Eventing Sport world wide, it is foolish to school CC without a coach by your side helping you and watching. We all need eyes on the ground, even Olympic Riders train with eyes on the ground.