Yeah, my big issue is, if I just want to sit and re-create a picture with traditional drawing techniques, I can do a bang-up job. Want me to draw that stock photo of an eye? Got it covered. I'm well-trained. There's always a benefit to revisiting your fundamentals, but that doesn't always help me with my comic art.
The break-down is in 'how do I translate this real-world thing to the more simplified style of art I use for my comic?' I cannot afford to draw hyper-realistic eyes/trees/fabric/whatever for every stinking panel. There are lighting effects that I cannot replicate with my markers, no matter how hard I try. (And I have tried.)
Maybe what I need is more of a 'draw this in your style' type of practice, doing studies with comic style instead of art class style.