One of the fundamental basics of game design is to help players not gimp themselves. If a melee player doesn't know his hit cap (which is very very hard to find out based on the game alone), he can easily get too much and gimp himself. The "fix" is to have lots of third party forums, articles, spreadsheets, and simulators to help people try to even understand their gear choices.
Though, if you think about it, the game also doesn't show you how well you do outside of living or dying. Mix in random effects that can kill players for "challenge" and you have a perfectly obscured system that has no measurable method of knowing how well you are doing or how to become better.
I challenge any raiding group in WoW to raid under these conditions.
- No mods. That means no threat meters, no decursive, no DPS meters, nothing.
- Each piece of gear that drops has to be worn by someone as you make progress through the content. Obviously, harder content means better gear.