ive noticed a similar thing as well - the corpus enemies seem to spawn out from 6 distinct areas
but i feel like this might not necessarily be a bug, more like a reason to rework the map(?) - in the grineer side, the spawn areas are similarly fewer compared to its non mirror defense counterpart, but the enemies arent as concentrated because the map is considerably bigger. besides, it doesnt seem like there are other locations that spawns can happen.
also, i've discovered that if you use Dual Ichor Incarnon form, you can get a high number of kills and XP without doing anything as toxin clouds eventually creep back and accumulate at the spawn points and starts spawn killing quite quickly.
After some testing and talking to a few people, we were inconclusive as to whether it is an actual BUG bug, because this is not an error in the programming code - it's just a result of the available mechanics working as intended, even if the kills might feel a bit lazy. And looking at the rate of XP, it doesn't seem too flagrant I suppose. On par with a Saryn in ESO. Anyways, thought I should report on that and maybe get an opinion from the devs because it feels reminiscent of the spin2win days haha
One problem the above Dual Ichor Incarnon interaction does lead to however is occasionally a massive, extreme drop in FPS for squadmates, presumably because enemies are dying and spawning clouds in the same place quickly. But it's weird because it doesnt always happen every time.
For other Tenno reading this, maybe it's best to hold off on using Dual Ichor Incarnon Form on the Corpus side for the sake of considering other peoples experience 😁, and my apologies to all those who had to suffer 4fps when I was still trying to figure out the cause of the problem