From what I've heard on Discord, the condition for sunder charm drops from Heralds looks like this:
"ConditionCalc": "\"cond('MonsterTestElite', herald)*(stat('heraldtier'.accr) >3) \""Credit to @Nishimura_Katsuo (the guy behind https://nishicode.com).
It's not entirely clear what ">3" means, but if you assume that the tiers are 0-based (0, 1, 2, 3 and 4), then it would mean that only tier 5 can drop them. Or, it could mean that it can drop from tier 4 and tier 5.
Also, the drop rates of sunders were apparently not changed. The difference is that in the past, all champions and unique mobs in TZ were eligible to drop one (as long as the TZ level was high enough anyway), but now it's only Heralds, and only the higher (highest?) tier, meaning they're now extremely rare compared to before. ~1/238 on p1 according to Nishi who has looked in the game files.
EDIT: MrLlamaSc has said on stream that herald drop rates will be tweaked (and I'm sure plenty other things will be tweaked too, just wanted to mention that as well).
ShadowHeart
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