Cleave and Power attack

[Nine Hands]

A [W] in damage indicates the weapon's damage dice. The number before indicates the number of times you roll the weapon damage dice.

Therefore a power that does 3[W] + Str does 3d10 + Str, if the weapon uses 1d10 and 6d6 + Str if the weapon normally does 2d6.

That is from the PHB, page 276.

 

[Deverash]

The first example on 276 of the PHB shows that you only add the modifiers to damage once, regardless of the X[W]. The [W] is what it says in the weapon table(where they talk about damage on the same page)

 

[small pumpkin man]

a 21st level character (20 str) using a greatsword, cleave & power attack does 2d10 +14(5 str, 9 PA), and the cleave does 5 damage.

"Any roll of the dice" means whenever you roll dice not every die you roll. It's not confusing unless you want it to be.