Max, your math is wrong. Here you go:
Whale has +15% attack bonus with temple (+7 Runes). There are 11 of these...Gallantry. So that's a total of +130% attack.
F2P has +6% attack bonus with temple (I think +4 Runes). There are 11 of these...Gallantry. So that's a total of +66% attack.
Now, say both have a level 40 castle and their archers (making up numbers here) have a base of 30,000.
Whale 30,000 x 230% (100% base + 130% bonus) = 69,000 attack
F2P 30,000 x 166% = 49,800
Difference in attack power = 19,200
Now lets say it's bumped up to level 50. We will use the same runes, but lets say that the power of archers doubles. Historically, going up from XII to XIII is a much greater boost than going up from X to XI.
Whale 60,000 x 230% = 138,000
F2P 60,000 x 166% = 99,600
Difference in power = 38,400
So as you can see, by increasing the base power, a whale (or anyone) with a higher temple gets and even larger power gap.