Where I was trying to go with my little rant was IF Turbine was to decide on putting in spoiler info into the quest entry GUI, then they also need to decide how they figure out the number to enter. While on the surface it appears simple, in practice it is not. Some players tend to take whatever appears on that GUI as gospel and immutable fact, and if it said 4, then they would never even consider it without four. Even if it would be trivial for 2 players to do it. Would you want Turbine to ASSUME use of Gold Seal Hirelings in their estimates? Then almost any quest would be easy to solo and even some raids could be (VON 5 for example).
A quest like Tear of Dhakaan becomes hugely more difficult at level if no one can open the 2 locked shrines. How about a warning on that one too? I understand some of the perspective of the OP, but I personally often expect to fail to complete a quest on my first time in and have to retreat to retool or grab other spells or weapons as best suits the quest. Perhaps that is why I am not at all bothered by the current setup.