As a general D&D problem, you simply use bards for comic relief.
As for half-elves and the other half-races, rather than making them about interbreeding per se, I like making the half-races "a wizard did it".
In particular, my current default is that an ancient empire made a deal with Devils, and the noble class became Tieflings as a result. They proceeded to do biomancy and generated half-elves, half-orc, muls, and other "hybrid" races as specialized labor.
This being ages after the fall of the empire, the biomancied races still exist. Elves and humans with no half-elf blood are unlikely to produce offspring, but half-elves who breed with elves and humans can produce half or full blooded (in appearance) children; those children may also carry the cross-species fertility ability.
As for half-elves and the other half-races, rather than making them about interbreeding per se, I like making the half-races "a wizard did it".
In particular, my current default is that an ancient empire made a deal with Devils, and the noble class became Tieflings as a result. They proceeded to do biomancy and generated half-elves, half-orc, muls, and other "hybrid" races as specialized labor.
This being ages after the fall of the empire, the biomancied races still exist. Elves and humans with no half-elf blood are unlikely to produce offspring, but half-elves who breed with elves and humans can produce half or full blooded (in appearance) children; those children may also carry the cross-species fertility ability.