I think that the best place to finish Destroyers is WOE (Wrath of Evil) under the Rathleton's Magistrate. Here you'll find dozens of Destroyers, and finish this position very quickly. I suggest to take an EK (as I remember you're an Elder Druid) to hunt there as duo, but starting from 600 level you could do it solo as well.
Another two places with some Destroyers are:
- Apocalypse Seal at POI (Pits of Inferno Quest)
- The Blood Halls/The Vatsat INQ (The Inquisition Quest)
These options are really nice if you want to finish your bestiary slower, but you want to finish it with other monsters, which you can find on these seals.
On the other hand I do not recommend places like:
- Asura Palace
- Grounds of Destruction
- Yalahar Alchemist Quarter
These places are shown on tibiopedia.pl:
https://tibiopedia.pl/monsters/Destroyer
Unfortunately you can see that amount of the Destroyers are really small (only 2-3).