Countess last ladder

The countess' special rune drops take the place of items that she didn't drop, so more item drops mean less opportunities for rune drops.

So we would expect that this ladder, with nodrop=0, it would be less likely for her to drop many runes. Last ladder, the higher nodrop setting would have allowed for more runes, as there would have been fewer items dropped. I would expect that bnet would have been even more so, though.

See https://diablo2.diablowiki.net/The_Countess#Rune_Drop_Specials

In particular:

Her Treasure Classes are uniquely modified, and as a result the odds of her dropping multiple runes are actually increased when there is only one player in the game. (Even though she'll never drop more than two items, her rune drops come from special treasure class sequences that are accessed if the game doesn't think she should drop other items. Since she's more likely to roll to drop additional items when more players are in the game, even though her drop is hardcapped at two magical items, this cuts down on her odds of dropping a rune.)

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I thought maybe it had something to do with last ladder changes being related to Resurgence but I'm not very familiar with that server.

I am pretty sure the servers are completely independent, at least for the purposes of this question. Maybe you're thinking of 'resurgence drop rates', which are roughly 1/2 the nodrop/player setting of bnet, kind of a compromise between vanilla and nodrop=0?