It's not corrupted.
You cannot understand their speech if you kill them without having done the questline leading up to killing them.
The problem is, the quests for a couple of these don't exist anymore, or were changed to have different quest IDs.
For Dyle:
It requires quest 2213 completed, which is part of the old Dyle questline (The Monster and the Evil Scheme), and the entire Dyle questline consists of quest IDs 2213 through 2221 (all of which are blocked). The new Dyle questline is quest IDs 2888 through 2893 (except 2890, which was blocked).
For Mano:
It requires quest 2153 completed, which is part of the Legend of the Snail questline, blocked off years ago.
For Stumpy:
It requires quest 2144 completed, which is part of The Old Tree questline (the old Stumpy questline). The new questline consists of quests 2813 through 2815, including the quest Stumpy the Ent (though they're Explorer only now).
As for Timer, they apparently removed the conditions for Timer's dialogue. If anything they should just re-add them. Then again, the boss dialogue system could use a rework entirely. For example, Timer has dialogue at 19,500 HP, which was fine back when he had 21k HP pre-Big Bang, but he now has 9.4 million health. That's a thread for another time though.
The reason is because there are 2 separate codex cards for Roid (one from pre-BB, one from post-BB), and the search bar sends you to the pre-BB version.
