Sorry, I can't recommend Borderlands. After four people praised it I looked for gameplay videos on yt. All your enemies take bullets like they are marshmallows. It doesn't seem deadly. The presentation is stylized and exaggerated like a cartoon. The sound effects are nice but the voices and acting come across as a hammy Hollywood movie with overdone acting and ewok language. The worst part is that the player has to bust a line after every critical hit with insulting, stereotypical phrases like "das what ah'm talkin about" and "whoomp dey it is."
I understand that the gameplay itself is chaotic, but not worth it imo if you have to put up with an army of things that make you sick. Perhaps you'd like Stalker: Shadow of Chernobyl or Metro 2033.
It's a gear looting based game similar to Diablo, so if your guns and stuff svck then yeah things are overly tough to kill, where you hit matters too obviously. Yeah it's a bti of a comedic apocolypictic world, so if you are looking for 100% serious business it probably won't be for you.
I passed on it for a few years until it came down to about $20, but I played it for a solid 2 months straight with a single character (once you beat it, it restarts you with your all gear/lvls still and on a harder difficulty), so it was more than worth it at that price and it's probably much cheaper now.
Not to mention the awesome co-op.
I'm not a fan of FPS either mind you (pretty much just Borderlands and Fallout), so it's got lots of RPG under the hood, particularily the loot that has fully randomized stats/attributes/special effects/etc on a scale that has not been seen since Diablo2.