CSM: What about a 5 pts drop because their boarding bonus is partly superflous?
As for Chaos Marks, agreed with Thane about legion limitations; restrictions for aligned legions obviously, but that's it.
As for Marks, like afterimagedan I feel like these should be allowed without a CSM/Chaos Lord/Warmaster. It just fits chaos, and it's not like they have so many cheap upgrades kicking around to clutter their stats
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Mark of Khorne: 15pts sounds fine, cheap but effective, could be more but a limited tactic so its fine.
Mark of Tzeench: 20pts sounds fine, ok on regular ships but extra potent on carriers (BFG:R profile of course)
Mark of Slanesh: 20pts seems a little steep for this, especially considering limited range. I suggest either boosting range or lowering price, as this becomes pretty useful if any ship can be marked.
Mark of Nurgle: 25pts is fairly steep for this; the extra hit is worth 10 pts, so 15pt for the ability to not be boarded? Most fleets just H&R anyways, so my suggestion is 20pts.
I think all fleets should use a standardized reroll price, on every single list IMO.
Again I have no real opinion on daemon ships, but have also heard they are crappy.