I developed a 2 year college program and I just really push the fundamentals. All of the trickery comes and goes but the fundamentals haven't changed THAT much in my 16 years as an AE user. Great shape layer keyframe animation, elegant parallax/2.5D/multiplane environments, comfort tweaking/nuancing animation in the Graph Editor, standard VFX compositing skills (track mattes, light wrap, optical effects, etc.) and 3D camera manipulation go a long way. My graduates tend to have niches that propel them to the next level but the fundamentals are the common denominator that they keep falling back on.
I don't know if that's helpful at all but those areas of After Effects are where most of my students find success and where most of my freelance money is made.
You said it yourself: Too wide and too far a field. If you were to do VFX, obviously rotoscoping and tracking would be more important than other stuff, if you were to get into broadcast design fast turnarounds on stylized graphics matter more. Beyond that my general observation is that most "AE artists" don't really have a handle on their workflows and from sloppy naming conventions to awkward constructs to create simple blending modes I've seen too much. In my view the latter is more important than anything else - you have to know how AE "ticks" and adapt your workflow is rather than trying to bend and mold the program. When you know that, you can do anything reasonably quickly. E.g. in my projects I've always isolated steps by using lots of pre-comps. People will then sometimes accuse me of over-structuring my stuff, but in the crunch, I only have to exchange the logo in a single comp, not delve into the other 20 again. That's the kind of stuff I always go for.
Cheers for the replies guys, that's exactly the kind of "real-world" info I was hoping for.
One of the more important things you get only from years of experience, yes, years, is the ability to plan your project intelligently and to estimate the rendering requirements.
Wait. That's two things.
And how rendering is affected by stuff like motion blur and 3D and lights.
Wait. That's three things.
The skills with the application can only be gained by slogging through hundreds of projects. The keyboard shortcuts revolutionize your workflow. But if you only do one or two projects every now and then you will never get it. Each one is a relearning experience, frustrating and inefficient and you spend hours looking for canned products to solve simple tasks and your work looks like everyone else's.
Learning the software is the easy part --- Learning how to make moving images that tell a story is the hard part. The next level is more about design and understanding how we perceive motion and story than anything else. I'd suggest you start taking your AE skills to the next level by finding something that isn't a really cool effect but is instead an amazing way a story is told in a 3 or 4 second shot and then break it down and try and figure out what makes that shot work, then try and duplicate it. You can even shoot the basic shot with your phone, then do something amazing with it.