I have to agree with some of this. Bioware stated that you could use any of the companions too solo through the story part of the game. I don't remember them saying you had too use a specific one just too
survive.
Played a Marauder too 25 in the beta, and I just hit 30 last night. I can say that it is getting better as I level up, but with that being said, it feels like a up hill battle till about 26 or so. I don't think you should have to play a class that long for it too start being fun. The other classes have a much easier time than we do.
I am Carnage spec right now, and have been since the start so perhaps that is why I have had a rough time with the class so far. Don't get me wrong it is fun at times, but it also makes me infuriated at times as well.
On a side note, I think people need to start being a little more helpful and stop telling people to learn too play or you suck. These are not the blizzard forums, and if everyone would help out and give some insight it would make all of us Marauders better players.