Since the latest patch, I have started a replay of Heart of Gold. On the first mission, not only are the hero spawns fast and regular, but they keep on spawning from destroyed gateways.
I was led to believe by the narrator in previous campaigns that destroying the gateways would prevent further spawning, therefore I think this is a bug.
I can confirm that this occurs from all gateways in the map, not just one of them. This makes the level extremely challenging, especially towards the end where the final portal (the hidden one) spawns and nothing but level 10's spawn from every gateway !!! Not even the most hardy of underlords can survive that onslaught!!
Save games are attached for reference
I've attempted to remove and redownload the game aswell as verifying integrity, for what its worth.
Intel Core i5 4690k
AMD R9 290X
Customer support service by UserEcho