The problem with multiple path and more open dungeons is that eventually there will be a "fastest/easiest/simpler path" and boom, nobody but those weird people running dungeons at min ilvl, or a new tank that does not know "the path" will ever take the other routes.

Sure, the solution here would be making the paths at random, a random path dungeon between some sets and order would be nice, say, you have 3 paths to reach boss 1, other 3 paths o boss 2 and othe 3 to reach boss 3, permutate the paths when dungeon start and even switch the boss order, that al leas will give you... 3x3x3x3 ways a dungeon could be ran, randomize trash mobs too and there, variety. Sure there are not player choices tho, but if players could chose they will go for the fastest way.