Yes, absolutely, in fact I'd argue companions can be as much of a hindrance as a help, as they often blow your cover, charge off into highly dangerous situations without a second thought or set off every floor-based trap you come across. Keeping them alive can become quite a task at times, as they have little-to-no sense of self-preservation.
It is definitely possible to beat the game without using companions at all, indeed this is the normal run of it, unlike say the first games where doing a no-companion run was an elite, hardcoe-only challenge. In FO3, you're the Lone Wanderer, after all. You're kind of meant to fly solo.
If I may ask, what in particular are you finding frustratingly difficult?
Ah, thank you SO MUCH.
That was what I was hoping was the answer, as I liked it better alone after just a few encounters with Dogmeat at my side. (Which is very different from 1 and 2, where I found I liked the companions). I think the big difference is, in 1 and 2, combat was turned base, and you could therefore plan around your companions, although even then Dogmeat tended to make explosives obsolete since he was always up close. In 3, it just doesn't feel nearly the same, and IMO feels better solo.
As for the frustratingly difficult part, well, part of it is my own lack of patience. It got real old fast travelling almost anywhere and being greeted with multiple tough foes. Once, when I fast travelled to one of the metro stops, can't remember which one, I was met with TWO MASTERS AND A BRUTE. At level 13 or 14. That was the one that had me, in a fit of disgust, uninstall the game. Come on, your screen just refresshes from the fast travel and you've got TWO Super Mutant Masters with miniguns blazing right off the bat???? And another brute was there too. I died quickly, threw up my hands (because it was just one of several times I fast travelled somewhere only to met with overwhelming combat odds right at screen refresh.
But the week off left me in a better frame of mind this time.
I realize when that happens that you just need to not panic, remember that the B button is your friend, and work through it. In fact, if you keep enough ammo and stimpacks, and remember to use the B button when needed, I'd guess it's actually pretty hard to die in combat. But I am still learning (and loving) this game. I think it's replaced my old ALL TIME FAVORITE game of any kind on any platform. For years that honor was bestowed upon Gothic and Gothic II (Gothic 3 svcked IMO), but this one I think has finally unseated that long time champion. Although Gothic will always have a special place in my heart.