Actually I've seen it maybe seen it only eight times give or take a time or two since 2001. I can say the times I've seen it I thought it was gamey roadkill.
When I played for the first time in 3 weeks last Saturday, I saw a HQ going down 4 times - 3x Knight and 1x Rook. I was barely able to save our (Bish) HQ, because the ib Lancaster pilot did not go NOE and I was able to spot early. Still it was a close call, as the Komet field is located at quite some distance on that map. It would had been impossible to stop him in a conventional, non 100 point plane.
In this particular map situation, the only way for Knights (and later rooks as well) to effectively"defend the HQ" would be a constant high altitude cap over it.
Who's going to do that?
"Just fly a goon".
Ni's had at one point 165 minutes downtime. One goon takes away 4 minutes. No think about what will happen at low times when there are less than 30 people on your country at all. Compare that stuff to the effort it takes to kill the HQ...
Don't get me wrong - usually I'm one of the "If you want to keep it, defend it" faction. But as I pointed out earlier, the combination of low player numbers, HQ placement, City connection and game impact vs effort necessary to kill HQ is very much out of balance at times.