Nope, that still doesn't compute. If districts are based on numbers, then geographic density doesn't matter because denser districts are just smaller. If Democrats are disproportionally concentrated in some districts (which is really what you're referring to), then the other districts will have disproportionally more Republicans. But if you define districts strictly by geographic proximity, compactness, and communities of interests, you will have districts that are fairly immune to the effects that can be artificially produced by gerrymandering.
Take a look at this Wikipedia illustration and assume that the green voters are Democrats geographically concentrated in cities. "Packing" is illustrated by the top right diagram, and it's what Democrats could do to win 60% of the districts even though they are a 40% minority: Without regard for geographic proximity, Republicans have been "packed" into districts where they have large majorities, but Democrats win more districts with small majorities. "Cracking" is illustrated in the top center diagram, where the urban area is deliberately split up and the small pieces and added to rural districts where they are outnumbered by Republicans, leaving Democrats no districts at all instead of their fair share of 40%. The bottom two diagrams are more like what would happen without such engineering.
[qimg]https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/DifferingApportionment.svg/720px-DifferingApportionment.svg.png[/qimg]
Again, nope, not unless you drop the two extra electoral votes each state gets. That's the source of the unequal representation.
