|I guess this guy is a little broken, isn't he?|
First of all, let's try to understand why some people think the rule is broken.
I'll use the Daemon of Nurgle special rule as an example. Because the Daemon of Nurgle special rule says that "Daemons of Nurgle have..." then some people take it to mean that any Daemon of Nurgle in the same army as a Daemon Prince with the Daemon of Nurgle rule instantly gain all bonuses that the Daemon Prince receives.
So what does this mean within our own Codex? Well, according to these people, if you give a unit a Mark of Nurgle, it then becomes "of Nurgle", and if it has the Daemon special rule it is therefore a "Daemon of Nurgle" and is as a result effected by the Daemon Prince's special rule. Warp Talons with Shrouded, anyone?
Because of a 15 point mandatory upgrade you now have one of the most broken armies in the game, right?
Why this is wrong is pretty simple really. The "Daemon" Universal Special Rule and the "Mark of Nurgle" are two completely seperate entities. It does not say anywhere, on any page ever that a model with a Mark of X and the Daemon special rule becomes a Daemon of X.
But why does the entry say "Daemons of Nurgle have..."? Because Daemon Princes are not a one-per-army unit. You can have multiple Daemon Princes in your army, and thus all the Daemon Princes with the "Daemon of Nurgle" special rule are "Daemons of Nurgle".
What about Codex: Chaos Daemons though? To be completely honest with you, I have nothing on that one. It is indeed very possible to argue that all Nurgle Daemons from Codex: Chaos Daemons gain the rules for being a Daemon of Nurgle, and whether this was intended or not only time will be able to tell. Unless I missed something, of course.
Basically: Daemon of X does not do anything for any unit from C:CSM but it might be a little broken when combined with units from C:CD.
Thoughts? Comments? Proofs?