Answer me this. Why would you go with P+K rather than 4P+K? Why would you extend the mixup when you can launch with another move that hits at the same height and is of equivalent speed? I for one used that move regularly. Now I won't be using it. Not in the same way at least, and using it in its new way seems unproductive.
Completely useless? Well, all moves have their uses, but it can be considered useless if there are other moves with similar speeds and even faster speeds that give better options at all ranges. The move was a nice gap closer before, now it's putting yourself in danger at range... Let's put things into context for a second.
If the opponent blocks P+K in the prior version, you'd have frame advantage, which would let you keep your pressure. If the opponent blocks it now, you'll be giving the opponent a free grab punish since it's unsafe.
If the opponent fails to block and it hits on normal hit, which rarely ever happens in a real DOA fight, you do get a nice stun, but it's nothing that 8P wouldn't give you, and 8P has follow-ups and mixups in case the opponent does block, making it a safer move than P+K for yourself, and a more hard to defend against move for your opponent.
If in the past P+K hit on counter hit, you'd get a launcher for immediate damage through a basic juggle. If it hits on counter hit now, all you can do is 6P or 2P, where the opponent has options to defend afterwards.
The move has been heavily nerfed, whether you accept it or not.