For world/map events that require using something that updates my skill bar, for example changing into a mushroom to blow up slime layers, etc, all of my necromancer minions: Bone Fiend, Shadow Fiend, Flesh Golem, etc are disbanded. After completing the objective all of my minion skills return however they are all on cool-down which is made even worse if you have to repeat the same event task multiple times.
If it is absolutely necessary to remove skills during world/map events, I think it is only fair that my skills return each time without a cool-down timer to exasperate the issue.