I agree, although I am about halfway through TVH mode totally solo. But I must say the game is really tough with my siren, even though I am technically overlevelled.
Just imagine how much fun it has been for me being
under-leveled through a lot of the content.
I also dont like that some of the skill trees force you to put points into multiplayer focused skills to get to single player skills that you want.
What I dislike is how some of the skills are just too niche. For example, Maya has a skill that adds fire damage to her shots but only during Fight for Your Life. That might come in handy, but you hopefully
don't fall into Fight for Your Life to begin with.

Personally, I would prefer to see it provide a smaller bonus all the time and a larger bonus during fight for your life. Something like +2% Fire Damage / +8% Additional Fire Damage during Fight for Your Life (per point). This would provide the same bonus while in Fight for Your Life, but make it slightly useful elsewhere.
I just fought Wilhelm, and it sure would have been nice to have a partner so one could focus on taking out the repair drones and someone else on taking down Wilhelm.
They did just buff Wilhelm, which I think was necessary. When I fought him with Gaige, he was a joke, and he actually
ran away from me. I killed his Surveyors right off the bat before he even reached me. Wilhelm is a pretty crappy boss anyway; in my experience, his abilities are too focused on melee.
Sure would be nice to get an orange drop a bit more often too. Unless I get some better equipment I dont know if I am going to be able to finish on TVH mode.
I've found a lot of decent equipment, or I've used a few golden keys every 5-or-so levels. I had over 40 of them, so it helped to have a slight boost in good gear. Keep in mind that one nice benefit of actually playing the content at the right level is the gear is
actually your level... it's just really difficult to kill the enemies to get it.

I think half of my current weapons were things that I found and the other half were from the chest. The rocket launcher that I mention below was one that I found in a chest.
Oh, and when you get there... consider farming Opportunity. I'm pretty certain that it has the most chests out of
any zone. I think there are two of them that you can get without even fighting enemies; however, you do need to be a bit careful with them. The one is the horizontal red chest near where the Super Badass Constructor spawns. The trigger for his spawn is in a weird spot, so you can grab it and leave with ease. There's also one on a ledge near the Hyperion Info center, which is right by the prior chest. It's possible to reach that without spawning the enemies.
I got my first 14k launcher yesterday, and I was tickled pink!
I didn't care much for Rocket Launchers until I found this Torgue one. What makes it different is that it has the uses less ammo attribute, which will make it sometimes not consume ammo. The biggest problem with rocket launchers is that your max ammo capacity is just so small, and ammo is so rare compared to other types. That attribute makes it much more bearable, and it has a 7-round magazine size (with my talent reducing it). If I'm fighting something like a Super Badass Loader, I might slag it, and run at it just unloading a ton of rockets. Its health just drops like a rock!