I have a 6ft and 8ft rod and even the 8ft can sometimes be a little short for rock fishing because you can't always be right at th edge of the water from the rocks.
A short rod with light line on the rocks is a recipe for lots of broken line, lost tackle and lost fish. Also bear in mind that every time the line breaks while fighting a fish, the fish then is stuck swimming around with a hook or lure and line stuck in it's mouth, which I don't think is very humane. I'd rather have a fish ignore a heavier line than break me off on lighter line.
For the lightness factor you're after, just remember that you will have to compromise, especially if you don't want to spend hundreds on the rod. Find a few of the right length that fit the line rating and cast weight you're after, and hold each one in your hand. Give them a good shake and see how they feel. Point each one straight up and then lower it to horizontal and then back to vertical. Once you've done that with a few rods, you should have one that feels right.