Arah is my favourite dungeon in the whole game.
However, Arah (bar Path 3) is no harder than any other dungeon, and only Simin in P3 makes it slightly harder. The reason I like Arah is because it's the best put together dungeon in the game, the mechanics in Arah surpass every other by a large margin, and the visual look of the place is amazing. It often feels like Arah was the dungeon they made first, and put a ton of effort into it, and then they ran out of time for the other dungeons and just had to put them together quickly by comparison.
However it's not FoW/UW level. It's no where near as big, and there is no sense of being in danger, as unlike FoW/UW if your party wipes you can just respawn at the last WP.
GW2 does need some high end, bigger party, elite content, and I look forward to the day it's added. I have great memories of doing guild runs through FoW, UW, The Deep, Urgoz, DoA, etc in GW1.
But saying that, we still find plenty to do in the game each evening. And tonight the next part of the 'Living Story' starts, so we're looking forward to doing that