The reason I started doubting whether statistics were everything was because I really could not theorize the number of manasources necessary in the aforementioned deck: it was just too complex to calculate due to all the cantrips, tutors and number of manasources I wanted in a given matchup at a given time. The only way to set the right number was by really testing it.
So: how important is real testing compared to analysing?
All budding deck builders will settle on a theoretical ideal for the number and kind of manasources their deck should have. Say, 24 or 25. Goldfishing will let you know if that number is at least do-able to accomplish what it wants. Then testing against other decks will let you know if the rest of your deck works off that mana base or not. (ie, is your deck filled with Waste Targets, do you get owned by Null Rods?)
Testing (especiall on a new deck build like DraGroNaught) is the ONLY way to see if ar mana base is adequate. You got to play it against everything people are willing to throw up against you.
Play play play, test, test, test.
In the Summer of Fish, I had to cut an entire color from my deck to fit in 5 Basic Lands into my deck versus a field of Trinisphere X4 Shop decks and Null Rod packing UR Fish decks. The amount of manasources stayed the same, but the type of mana changed.