I agree that having a little dihedral isn't necessarily a bad thing. Dihedral also put the center of effort of the paddle slightly behind the axis of the paddle shaft which makes it more stable when pulling on it.

: The theory behind dihedrals is that the water vortexes will be split at the
: dihedral and spill evenly off of both edges. Otherwise, they traveling
: back and forth across the paddle face, spilling more off one side, then
: the other, causing fluttering.

: If you can create a paddle blade that has decent thickness in the middle
: (thin at the tips, though), you get more buoyancy, less tendency to dive,
: and easier rolling and bracing.