Yes its some cases you don't want them like quests there you have to kick someone down to 30% health and use an spell on them and Ember uses execute.I just have the companion I currently use quickslotted. Activating them again will unsummon them.
How do I get rid of a companion nowadays? Used to be that summoning an assistant did it, but now they come back after each loading screen. I keep losing rapport when doing black sacraments for the event...