There seems to be a bug with both quests.

With Adding Injury to Insult I'm able to get credit for the first half but not for defeating him. I've tried leading him to Lydell and just killing him myself and neither works.

With Apply Heat and Stir, I'm able to fill the empty flask, and mix the Vrykul blood with the samples but then nothing happens and the item disappears from my inventory. I know the quest has to be done repeatedly until it is successful but the item disappears after the first try and I don't get any credit.

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https://www.wowhead.com/wotlk/quest=...-heat-and-stir
https://www.wowhead.com/wotlk/quest=...jury-to-insult