Bear with me, and apologies for no visual representation here. ElvenArchitect is blocked at work. But the benefits seem astronomical compared to Willows, so I'd love a sanity check in case I'm not thinking about numbers correctly. This ignores culture, coins, supplies, etc. that these buildings all give, plus road culture.
No Event.
Build 10 Weeping Willows. At 5x5, plus 25 squares of road (for simplicity - assume I don't make better use of the 4 road squares at the end of "Willow Row"), I'm spending 275 (=(25X10)+25) squares for 1,860 mana/hour (tooltip says Willow is 186 mana/hour). That is 6.76 mana/hour per sq.
Simple Event Buildings.
Win as many Frozen Temple as possible.. Build them in a "Mana corridor."
Frozen Temple = 45 mana/hour. At 2x2, plus 1 square of road, I'm getting 9 mana/hour per sq. Very nice upgrade over Willows, though admittedly I'm only collecting twice a day.
Perfect World.
Build the Frozen Giant Shrine (5x4), and wrap 8 Frozen Fountains around it. On one end, you have 2 fountains flush against the 4-wide FGS. You then put 3 fountains on both the top and bottom 5-long side. You add 1 fountain on the last side, and have 1 square open for a road.
The FGS is 20 squares of dead space.
Each Fountain is 112.5 mana/hour (=2700/24). Connected to a set building, that jumps to 270/hour.
Each fountain is 2x3, so 48 fountain squares, plus 2 roads, and the FGS is 70 squares.
The fountains are producing 2,160 mana/hour (=270*8). I'm thus getting 31 mana/hour per sq. That's 5X better than Willows, and 3X better than stand-alone event buildings.
Now, am I reading the set rules right? Is my graph paper layout matching the building realities? I'll try ElvenArchitect tonight.
The "Perfect World" is incredibly efficient if the whole FGS is surrounded by Fountains. If I only get 4 Fountains, for instance, the layout drops to 23 mana/hour per sq. Still great, but not world-breaking.