Actually the WGr 21 cm Bord-Rakete was adopted from the Wurfgranate 42 21 cm mortar shell. It had an extremely high max ord and rather slow velocity. This made them extremely difficult to aim. They were not very successful.
The Luftwaffe's primary Air to Ground weapon was bombs. The most common sizes were 50 kg, 250kg, and 500Kg.
SC (sprengbombe-cilindrisch) - General Purpose bombs with a yellow recognition stripe.
SD (sprengbombe-dickwandig) Known as "Splitterbomben" were fragmentation bombs especially intended for anti-personel use but also effective against light fortifications or ships. They had a red recognition stripe
AB - (abwurfbehalter) - containers for SD-2 anti personnel cluster bomblets and SD-4 anti-armour cluster bomblets.
Late in the war Panzerblitz rockets were developed by using the R4M rocket motor and the PanzerSchreck warhead. Just how widespread their use was is debatable.
They were primarily Air to Air rockets used to break up the bomber formations. The rockets were even more inaccurate when used against ground targets.
Here is some good information on Anti-tank aerial weaponery.
http://www.quarry.nildram.co.uk/tankbusters.htmAside form any actual bug, the only thing AH doesn't model well is the ability to jettison the tubes and their supports thereby restoring the Aircraft's full performance IMO.
Crumpp