On my first playthrough, I think I finished the main quest when I was only level 31, at which point none of the DLCs were even released yet, nor did I spend much time with any of the companions other than Deacon.
It was only later on, when I was well established, did I make an effort to spend time with the other companions.
Purely from a gameplay perspective, I can do without any of them, especially the dog, but they add flavor and are part of the experience.
