The Chain argument is about the ability to function. If you are over populated you cannot attack or do thief ops. Mystics can still cast spells while over populated, why feeding runes to an Undead Mystic at the bottom to LL your top size players works to this advantage. Like most top kingdom play, chained attackers become mages and are fed runes because the cost of their spells are greatly cheaper and its based upon WPA and not guilds.
If you are using your rogues to target my Undead Mystic instead of hitting the attackers in my kingdom or my pure mages, then I have done my job. It is a support role, its clear you have no idea how synergism works in a kingdom. 3rtpa seems a bit low even for a hybrid and most provinces still run WTs to reduce the damage of the ops.
Most good kingdoms target bocans or rogues in general during the hostile wave, reduce their defense. Hybrid undead either mystic or rogue are accessible to easy hits and if they became a problem could easily be massacred or just chained down to ineffectiveness.
As for science advantage, not sure if you have this problem or not. But I know being Undead with access to revelation has made me an unwanted target for abducts. Orc Clerics are ruling the age with over 80 nerds because they can get good gains and undead with poor science even more at a disadvantage losing all their science to easy hits and inability to create elites unless traditional marching.
Also, you stated an undead core. I am merely talking about 1-2 support roles not a whole kingdom. Most people would avoid a whole kingdom of undead and only a kingdom with high orc or avian might attempt such a task and just try to out gain you or out hit you. Once again, if you are over populated you cannot attack or do ops, so just normal chains til you are down and out like you would any other attacker.
Cannot imagine an undead core lasting very long in a long war due to attrition. In war build you don't make much money and a few bocan and a handful of decent WPA can greed and riot the whole kingdom. Plus add in sapphire dragons and rituals and you can negate your knack. Just my thoughts. Good luck in your age and the point of this thread was to help someone with their Undead Mystic not talk about Undead Rogues and NSing and unusual Undead Rogue Cores.