This was linked to me in a complaint about Jack drops.

By minute 5 RedEagle has killed 85 metal in units and lost 1434 metal. The enemy team does not seem to be going out of their way to counter him.

By minute 6 RedEagle has killed 595 metal in units and lost 2934 metal. The tally so far is a failed Jack drop against a commander, a failed Jack drop against a different commander, and a double Jack drop against the same commander that only managed to kill some raiders and a bit of economy. A Thunderbird defeated the double drop, but a TB by 5:30 is hardly an extreme build with no other applications.

At minute 10 there is an effective Jack drop.

The overall cost effectiveness of RedEagle jumps to 8158 value killed, 5845 value lost. But I think this was more a blunder by South than an inevitability effective raid.

• The gap in air coverage let the Jacks get through in the first place.
• A lot of bombers were killed by the Jacks due to perfect timing, and with quick response by the defenders this could have been avoided.
• The Jacks killed a lot of Swifts as shot their pew-pew guns at the Jack, which seems sub-optimal.
• Two commanders hung around rather than running, one died.

I think only a few bombers and two factories had to die there. The rest was salvageable.

Looking at it economically, 3600 metal in reclaim was left in the enemy base, so in the end RedEagle did about 7.5K damage for the price of 3K metal, and 3.6K metal left in reclaim. It was effective on an economic level, but not wildly so. That said, knocking out the enemy air player for a while was a pretty good strategic outcome.

At around 13:30 four more Jacks arrived at the same position via the same route. They killed a factory, a commander, and a few other units. The score is now total killed 12.4k, total value lost 8k. Disrupting the reclaim was a pretty good plan, and there is now 5k reclaim in the area.

A massive drop with Gnats around minute 17 is the nail in the coffin.

The other fronts are independently not doing so well though. Also there is a questionable decision by South to invest heavily into Athena rather than reclaimers or counters to Jack.

If this game is representative, then I'd say that Jack drop seems viable but not so powerful that I would nerf it at the moment.

Jack would concern me the most if it had a large impact on the early game, as it is difficult to coordinate a response early and a large early advantage can snowball. But this game seems to show that Jack isn't a problem in the early game, as the first three drops failed pretty decisively. A commander and some miscellaneous units seemed sufficient to fight one Jack reliably. The double Jack drop was defeated with only a bit of support, and no dedicated counters were made.

The oversimplified version of the game is that Jacks were useless up until they won the game at minute 10. This is a big simplification though, as the drop cost 3k and a lot had to go right for it to work. I think it is fine for there to be risky, potentially powerful, midgame strategies like this. A cloaker would do something similar, as would a sneaky Djinn or Athena. It's also worth noting that the sudden arrival of 3k in army value would have a large effect on any front, although the effect would probably be less flashy. Even something more global like a Likho, Missile Silo, or half a Bertha would have an effect.

There is an argument to be made that RedEagle could have saved his first four Jacks and done the 10 minute drop at minute 6, rather than throw them away in three failed drops. This is concerning, but it seems complicated enough to wait for an example rather than try to nut out whether it would be effective or not. A point against the strategy is that Jacks are pretty easy to kill if they have to walk long distances in the open, so if they don't land on 3k of stuff to kill, they're going to have trouble making back their cost. Another reason to be wary of theorycrafting here is that, while North could have Jack dropped better, South could have also done a lot more to counter the Jacks.

In short, the overall effectiveness of midgame Jack drop compared to similarly costly or risky strategies seems to be ambiguous and contingent on a lot of stuff going right. Early game Jack drop just seems bad, so it seems safe enough to wait until it is more explored. If you think it's so great, try it out.