I've been looking at the damage charts and noticed that the WG21 is assigned "200 of HE" damage while the RS82 is assigned "83 of HE" damage.
The WG21 has a 90 pound HE charge.
The RS82 has a .8 pound HE charge.
I've also noticed the WG21 explodes at d1050 while most action reports reference much longer range settings as used in actual combat.
Was there a day of infamy where WG21 laden planes ran amok unbalancing the arena which required dialing them back?
First, remember that damage done to OBJ and damage done to aircraft and gv's are 2 different monsters. No, you didn't specifically ask about that but I'm mentioning it just to make sure everyone is on the same page.
Second, it is all based on the scale of "# of X to destroy an 312 lb OBJ". While I've not seen HTC specifically express this as a base scale, I believe it to be plausible. Where we see a difference is on the "heavier" hardness settings such as hangers, shore batteries, HQ, naval guns, etc. As HTC has it set up, it will either take 2,3,or 4 rockets to destroy an 312 lb OBJ. Same goes for tank HE rounds ('cept the M8, it takes 11 HE rounds to bring down a typical OBJ).
Thirdly, a better scale to compare the rockets used to target ground effects is the German 28cm "Wurfkorper". This is the biggest kid on the block in AH in terms of rockets used against ground targets. It was loaded with roughly 110 lb of TNT and had rough range of 2400 yards, iirc. HTC has given it a damage value of 285 lbs. In contrast, the smallest of the true HE ground-pounder rockets in AH is the Soviet RS-82, and it has less than 1 lb of explosives, and HTC has given it 92 lbs of damage.
While I agree that HTC's scale of damage does not accurately represent the scale of differences in the real rockets, they need to apply a scale somehow and that is the route they've taken.
I think it is obvious that based on how much the 28cm rockets are used: the SdKfz 251 armed with the 28cm rockets is not worth taking to an enemy town thanks to a couple of things: the lack of being able to manually aim the launcher (sources say a minimum of °5 to a max of °45), and the inability to destroy buildings with 1 shot. In the real deal, the German 28cm rockets were known to demolish buildings with great ease, the battle of Leningrad showed that and there is plenty of testimony. Also, the M4/75mm Calliope offers a much better chance of survivability.
In the case of the RS-82, the I-16 is the custodian of 6 of them, otherwise the IL-2 can carry 4 of them. Not much in terms of platform offerings, really. I think it is rather obvious that the US 5in HVAR's rule the roost in terms of air to ground rockets thanks to the P51D, F6F, F4U-D, P47D-40, and P38L. The British Typhoon and Mossi can carry 8 of the 3in rockets for a whopping 1496 lbs of damage, but the rails scare most of the plane performance micro-managers away (same guys who fire their 110 rear guns empty, or the 4/30 cals in the Mossi empty, etc, to "save weight so they can turn tighter"

).
In terms of the range of the WGr21's, I'm not much help there. Once upon a time I used them in a 110 just to see if I could get good with them but my success ratio was far lower than just using the guns. This I do know: HTC has the timer or range set to go off at roughly 1200 yards. It is very difficult to gauge that range because we dont have a 1200 yard icon. The ebst way to test this is to get a squady in to the TA and have the friendly icons show you actual ranges, have the squady report back impacts and also watch the film.