Overall, this is a great update.
Here my problem with the slayer updates:
By increasing the abyssal demon at Kourend, you're making this a barrage/chinchompa task, the only one worth doing with it. Dusk devils dont have enough spawns/spawn fast enough to be worth using barrage/chinchompa. Nechrayels in Kourend are only greaters and doesnt count as a nechrayels task. Due to this, everyone who want to grind slayer with the best experience rates will be forced to go abyssal demons. Even though you buffed the experience rates at abyssal demons, you made it more popular and by adding dusk devils and nechrayels, it takes about 2-5 more minutes to get a new abyssal demon task. So, due to those indirect nerfs, the experience per hour is ruffly the same as before, even less. On top of that, we struggle to break it even in profit due to the runes cost. So same or less experience rates as before at abyssal demons and doesnt profit at all anymore.
Your second best option for slayer now is Smoke devils since it is multi now. Which mean, you can use a cannon there. On top of that, you made it so we can do smoke devils by doing a dust devil task. By using the nerfed blowpipe or chinchompa with a cannon, its about 200-250k exp per hour there. So, it is basicly the same experience rates as using a cannon at the old kourend abyssal demon , but atleast you would make profit by killing abyssal demons with casket/ensouled heads/whips. At smoke devils, the cost is rediculous. There is not enough consistent drops to break it even. Your only hope is to get lucky with occult necklaces.
I just feel like slayer is ruined now. You cant try to copy osrs slayer meta when you only have 1 spot/world man... anyway, overall it is a great update