I learned something new.
There is a column called `raid_target` in the `npc_types` table.
Code:
select * from `npc_types` where `raid_target` > 0;
I'm unsure the accuracy of the values in this column as I have never used it to make selections.
EDIT: It appears my database does not have any values outside of the default value in this column. Your DB version will determine if you have values in this column. I have the last cavedude DB from February which has values of 1 for some/all? raid_targets.
EDIT2: The list is incomplete from the February DB. It lists npcs from PoP and GoD. Not all npcs in this list are actual raid bosses indicating, if this column is used in the source, that it may be used for resting regen instead of merely identifying the npcs. It's a start for you though.