I have seen a flood of those lately. Call them "lopsided" dungeons, I guess. There are a number of variations with all of the rooms crammed to left or right, top or bottom, or filling a corner. There is also a variation that goes from east to west through the center with every room packed in tight.
The three main advantages are:
1) Minions have to deal with overlapping fire from multiple rooms at the same time.
2) 75% of mine entrances too isolated to use.
3) Can be difficult to earn 2 star because mana is spent quickly either making entrance or raiding heart.
1) Deeg attack to the unguarded (or lightly guarded) backside makes for easy 1-star.
2) Thunderbolt stun followed by Mistress and Troll rush can quickly knock out 3-4 defensive rooms because they don't have far to walk.