Ok, step-by-step calculation using
the formula.
Scenario without Multiscale:
Neutral natured Terrakion with 252 Atk EVs vs Neutral natured Dragonite with 0 HP and 0 Def EVs
All IVs are 31, lvl 100, Stone Edge, no held items or modifiers.
Terrakion's Attack is 357
Dragonite's Defense is 226, HP is 323
((((((100 × 2 ÷ 5) + 2) × 100 × 357 ÷ 50) ÷ 226) + 2) × R ÷ 100) × 1.5 × 2)
So it's
402 when random modifier is max and
338 when Terrakion is out of luck.
However, if we do not round down after applying STAB modofier, we have 169.5 * 2 = 339, so that's probably where Super Basic's error is.
Now if we give our Terrakion LO:
The formula is almost the same:
(((((((100 × 2 ÷ 5) + 2) × 100 × 357 ÷ 50) ÷ 226)+ 2) [134]
× 1.3) × R ÷ 100) × 1.5 × 2)
Results are:
440 - 522. So, this time, only Honko's calc is correct. And I have no idea where a lesser number came from...
Scenario with Multiscale:
Assuming Multiscale applies the same way Filter and Solid Rock do (this needs research however), we simply need to divide numbers above by two (and round down of course)
Without LO:
169 - 201
With LO:
220 - 261