How many people are going to invest the 500 or so hours to even get close to the WKC plat? How many people are willing to sit through the boredom of grinding the same quests for hours on end just to hope an item with a 0.5-1% chance drops? Don't forget that once you get to Guild Rank 8+, it's going to be hard to solo (pretty much nigh impossible) any quests, except for maybe a handful.
There are plenty of games that have 4 stars that just take a long time. There's nothing real difficult in Disgaea 3, but it does take a long time (and a big grind) to build your characters up enough to tackle the end-game stuff. Sacred 2 is another game that isn't inherently hard, but has a long grind time to get yourself through the difficulty levels (which can be bypassed pretty easily from what I understand).
