I could almost have taken your post and this thread seriously if you hadn't said you are running an arcane archer that does awesome DPS.
Here is the thing, if you start out playing DDO and you are seeing 5, 7, 4, 16, 3, 2, 5 go floating over the mobs as you fight them, then when you start seeing numbers in the 20's or 30's you think you are doing awesome damage.
And, when you start the game with weapons from Korthos Island and finally pick up random generated loot with multiple procs so that you start seeing 2 or 3 or more floaty numbers per hit -- then you're in high cotton as we used to say, you're really doing serious damage now.
So these players are not intentionally gimping themselves. They are just following on with the things they are learning about the game as they discover them. The 4 fighter 2 monk gives 5 additional feats. Not a stupid thing. The shield and bastard sword gives glancing blows. Not a stupid thing.
Does it all work together to create an uber build. Not by forum standards. But in that player's experience? Probably so.
And, to address your question directly, it is probable that the vast majority of players do not research their builds before they start them. Most players don't visit the forums so anything found here is entirely lost to them. I regularly run into players, many with epic characters, who either don't know the wiki exists or who don't use it even though they do know.
There are a lot of people whose fun is tied into discovering for them self. We can bad mouth them all that we want. But the truth is that they really aren't hurting anyone.
Did you complete the quest -- clearly you did, multiple times. So what harm was done?
Could their build be better? Sure. But they probably don't want someone they don't know being critical of it and offering advice. How did you feel when I started by saying that I couldn't take you seriously because you're running an arcane archer? Did it make you a bit upset, wanting to defend your build?
Leave the players alone. They'll eventually figure things out. And until they do, as long as the group is completing the quest it isn't really causing harm.