Angela, What you've said is good food for thought. I agree with you that if you really want to be a competent
permaculture designer, you can't just rely on a PDC and expect it to get you there by itself. Before, during and after a PDC, you have to be doing some related activities and reading up on
permaculture stuff that interests you.
People are so different and permaculture is such a broad subject ("natural systems and how they work," i.e. everything in the universe) that I think there are as many successful paths to getting to be a good designer as there are people. Each of us will no doubt find themselves lacking in quite a few areas and have to do things to bone up on those. Some are really important to be a good designer and some are less critical. Some people will come to a PDC with a lot of knowledge and skills previous to the PDC that are useful in becoming a permaculture designer, and maybe the course gets them to 100%. I think this is a fairly common situation. Personality, learning style and work history are all really important to consider, I think, for anyone who's trying to figure out what's the best path and a timeline I suppose for them to become a permaculture designer.
The world needs a zillion permaculture designers and it needs them yesterday, though, so I would do nothing but encourage people to dive in and yes, take a good PDC sometime in the not-distant future. If you're interested, I'd say get the ball rolling pronto however works for you.
Personally, anyhow, I'm finding that the 2016-17 version of the course, combined with the support of its online community, is about as good as I reckon a course could possibly be. Sure the subject matter of Permaculture is overwhelming.
Bill Mollison even said he had huge gaps in his knowledge. He didn't let it stop him, lucky us, and we can't either. Between permies.com and the online community of Geoff's PDC, both places of which have loads of super-helpful, experienced and knowledgeable people ready to help you out of any sticky situation, you can get a darn lot of great insight on almost anything that might come up.
If you don't have a permaculture mentor in your area to accumulate experience with, I wouldn't hesitate *if you feel ready* to strike out on your own as a designer after a PDC. Of course it's important to use your noodle, be responsible and ethical, and know when and if you're in over your head. And then ask around your
permie communities, bring in "ringers" to help you with the
project, or whatever. I think if you feel 50%ish prepared to do that coming into the PDC, I really think the course could get you the rest of the way, at least to make a start at it.
I wouldn't worry much about the possibility of making mistakes, either. You will.
Geoff Lawton still makes (and acknowledges, and learns from) mistakes on his designs. Mistakes are part of a lifelong learning process, and in a "live, soft" science that is as broad as Permaculture, they are inevitable. There are far too many factors involved to ever have a design locked up. But we have to remember we can make some spectacular improvements too, just by doing some really simple things. And it's important that we get out and do them. We have lots of people to ask about aspects of a project we're not sure about.
My overall strong feeling is that I think Geoff's online PDC this year is one of the most exciting courses I've ever taken on any subject: broad-ranging, mind-blowing, challenging, fresh, well-organized, surprising, supportive, comforting, beautiful... If you're in the right place for it, it's a fantastic choice. And in that case, it can prepare you as well as anything could, to go straight out and do good Permaculture designs. Each of us needs to add the part of being smart, ethical and responsible about it. And face the inevitable difficulties with the help of the support communities it gives you access to. We all need to start somewhere. And the rest is lifelong learning.