Octavia became a solid permanent fixture in my game. When equipped with a maximise spell rod item, and the feats built around enhancing damage dealing spells, like evocation spell specialisation,and ranged spell hit chance feats, she utterly kicks ass later in the game. Maximised fire ball spells and their variants make things much easier, just keep her equipped with a bow and out of range and she will be alright. I never used the half orc though. I am the same as you, I find it a real wrench to drop staring companions for other after a few hours. I never used jaethal myself though, I got Linzi, Amiri and Valerie as my staring group, and I eventually made a druid mercenary to add to the group, for another animal companion slot.