almost 100% certainty that the spawns haven't been halved
This statement from me is wrong. I just did a bunch of test with 1212 and the newest version and my findings are as follows.
With no interference in 4 runs (I stopped after 2 of each cause the results were pretty clear)
It takes the dragon about 1 min 22 sec to 1 min 36 sec to die, on both 1212 and the newest version.
The amount of spawned units is roughly the same, with a bit of non-important variance.
Its when you start killing stuff things go absolutely bonkers. On my t0 x2 (no T1 yet) character, I apparently kill fast enough to trigger the timer, but I do not kill fast enough to actually stay alive and kill the enemies. I have tried dozens of strats but no matter what I do (even on my T1 geared char), I end up dying which diverts all agro to the dragon which dies at an avg around 48 seconds. I might be doing this wrong, but the swarm is so strong.
I could really use a spoiler tag for this imagery.
With amounts of mobs looking like this: