As it the case with most things, the truth is probably on neither end of the spectrum being discussed. The scenario is not totally broken (with the designer-acknowledged exception of the Blocking Wargs infinite loop, an admitted oversight). Neither is it aptly-described as simply a challenging scenario which rewards players for thoughtfully constructing their decks. That description fails to capture the heavily luck-dependent path to victory of any successful attempt at this scenario.
I think at present, even the perfect deck will fail at this scenario more than 50% of the time. Can anyone claim better performance? Or even a 50% win rate? There are some very smart players on this board (many who are pleased with this scenario, I will add). However, even with their insights, there has not yet arisen a strategy for tackling this scenario that does not depend on optimal draw from both the player deck and the encounter deck. Therefore we can only describe Into Ithilien as a challenging scenario which requires both advanced tactics and a lot of luck. And honestly I think if you sit down and play 7 games in a row, winning only 1 of them, you cannot credit yourself with great tactics or deck construction for the win. You have to credit beating the odds and pulling just the right cards, which is little testament to the skill of the player. However, that skill has to -- has to! -- be present for the perfect victory conditions to ever present themselves in the first place.
I like what Valryian Steel said over in this thread: "Every card in this scenario is just brutal and there is absolutely no breathing room." Very succintly put.