Seems fine to me. I'd try to wiggle a Warrior Priest in there just so you have some more buffs going on-- you could even cut a cannon for it. The army runs on beating stuff to a pulp in close combat with the greatswords and flagellants... two cannons to back that up to get rid of really big monsters and monstrous infantry units that'll mow through the Greatswords are plenty, I think.
I'd take Lore of Life over Beasts. Your units are already plenty hurty with Flails and Great Weapons. But nobody's wearing functional armor-- even heavy armor on its own is one of those "makes you feel better" saves that doesn't really help much. But raising models back and raising their toughness both keeps the unit in the fight and makes the fact that your armor sucks a lot less important.
I'd consider giving the Greatswords the Razor Banner, if you can find points for it. I mean, if you're going to do a deathstar, you might as well go all the way with it.
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