The fact that you have no idea what happened is why this post is so hard to read..especially since you got invaded by the npc lol.. god..
What?
The quintessential Dark Souls experience is overcoming seemingly impossible challenges, sure, but that needn't be limited to soloing bosses.
I would never say not leaving yourself susceptible to invasion ruins the experience (Because I HATE being invaded), but I'd say at the very least don't just play offline and miss out on the bloodstains, notes, echoes, etc.
Hell, drop a summon invitation while you go farm, help a fellow player out after you master an area.
Should be enough simply not switching to human form unless needing to kindle a bonfire, and then killing himself afterwards. I agree that summoning people can take the challenge off a fight, although I've never had such an extreme experience like that (then again, I barely summon anyone ever). I did cave in and summon help to cut goddamned Kalameet's tail.
This might simply be your limitations as a gamer. Either up your skill or move on. Watch a youtube video of Sen's just to see how someone can trivialize it. If you can't replicate that, it's alright, no need to bash your head against the wall.
That's nonsense. Anyone that has reached Sen's Fortress can finish the game. It just takes getting better and more experienced at it. If all else fails, I found the lizards, along with black knights, to be the enemies in the game most affected by you being above their level. When you get back to Sen's after, say completing Anor Londo, man, they're such pussies.
Part of it is that they can one or two-shot you when you reach Sen's (unless you're overleveled, I guess), so fighting two or more at once is almost certain death. They're extremely vulnerable to backstabs, though, and there's often arrow traps that can be used to nail them (one right at the begining of the fortress, even).
Parry riposte you Lizard fucks!
Found the bonfire.
Rock rock.
Awesome!

Keep up the good work, we're rooting for you!
Cause I need it to beat the
No, you don't. I didn't even use a single ranged weapon on that fight, it conveniently parks itself on the bridge every now and then so you can beat the crap out of it with your favorite melee weapon. How polite, right?
Starting up a new character, it's amazing the gameplay and lore hints the NPC's give if you care to exhaust their dialogue options.
Talking to NPC's and reading item descriptions, you're made aware of enemy weaknesses and what dangers may be in what areas, and more.
I also noticed how From attempted to make Taurus an easy fight. On the way there, if you're attentive and explore a little, you will find lots of firebombs, even black ones, and also some pine resin, all of which are very effective against him.
Embarrasing story time: I was stuck on Taurus for a few hours, because I thought all of its attacks would be unblockable at that stage, and tried to learn the dodge timing to perfectly dodge through the entire fight. Turns out you can block most if not all of its attacks, they take next to no endurance.
The most embarrassing part? This was my second (non Game+) playthrough. Being used to powerful-looking attacks being mostly unblockable in the mid to late game, I just assumed this would be the case too.
