The manticore either needs to be incredibly cheap, given an armour save (or some way to icnrease resilliance and durability), treat like minor mounts and blend their stats with the lord or a mix of the above.
They are literaly a liability for characters whilst simultaniously making them a bigger target and alot richer.
"He who studies evil, is in return, studied by evil"
If we want to make this game "realistic" in a chaosy way, we need an unlimited table, and every warrior in the army rolls separately. Every last marked one. And, just to make it a bit more complicated, every God has his own table or six. We don't want this game to be too complicated to play. I say each Mark should grant a minor buff, or a bit larger buff and a minor debuff, but keep it simple.
Or let's take an even easier solution, have specific units for different Gods, like Daemons and Chaos Marines do. This way, each God's unit is different, even if they use the same base idea. It's like having Marks, but made clearer and easier. As much fun as random effects are, you can have too many in one list. When I play, I don't want to have a notebook next to me all the time. I hate having to make notes during a battle just to keep track of who has what. Currently I don't need to, as mostly only Chosen get more than one roll on EotG, which works well enough. Heck, even keeping track of Dark Eldar pain tokens annoys me a bit.
"Horrors are Pink, Horrors are Blue.
Where once there was one, Now there are two!"- Liber Malefic -