I only have one issue with the list, it doesn't have enough staying power. Any shooting army is going to be dropping rhinos and cultists like flies. Especially if they have any important vehicles that need to get their they will probably shoot the Melta rhinos out turn one forcing you talk walk across the table. The Land raider can be ignored because there are much scarier things in the list, like the maulerfiends which, granted, aren't super easy to crack open but even an immobilized or weapon destroyed result can ruin them. Juggerlord and flesh hounds always a great choice, nothing to say there. Back to the Land Raider, once the cultists get out with the Herald they will probably kill anything they come into combat with. However, you have to go through overwatch first and then if you charged through cover, your opponent attacks first against WS3 T3 6+ save cultists. If they make it far enough to slaughter something, now they are out in the open and your opponent can shoot them up.
So, here are my suggestions, take all of the cultists out of Rhinos, there job isn't to go up the field really fast, even if on the last turn just to grab an objective. They exist to wait in your deployment zone or in reserve to grab objectives in the last 2-3 turns. I feel like a land raider is almost always a bad choice only because it costs so much just to deliver troops. If it was about 115 points cheaper and wasn't a heavy support choice then yes, I would take them all day.
On the subject of Heavy Support, I know you said you didn't like soul grinders but they're so good in my opinion! The S8 AP3 pie plate scares people into dealing with them, which allows all of your other stuff to move forward, if they don't shoot the grinders, it allows them to march up the table till they get into charge range to beat stuff up. But again, I understand that you don't like how they function with the way they play which I totally get. But I have an Idea for you, next time you play try using two soul grinders and two maulerfiends in the same list and see which one functions better. I used to always use two in a list until one game I played them and Soul grinders and started to see more use in soul Grinders.
I would also recommend that you run some units of one chaos spawn, to eat overwatch/shooting, be scary, slap something around in combat or give a blood tithe. They are pretty cheap and not super easy to take out with T5 and three wounds, especially if you keep them in cover. One last thought, you have 130 points left over in your list, why not take some bikes or flesh hounds or something? When it really comes down to it, play what you want to play, not what I or anyone else says you should. Sorry if any of this sounds rude or harsh, not my intention. Have a great day!