Unfortunately, unless Hagakure is reverted to its previous form, Sam will never be able to line up properly with buffs without wasting a few GCDs as filler. It's been buffed slightly so using filler doesn't hurt quite as much as pre-5.1 at least, but you still want to make sure you fall into that buff window.

The only really exception to this are high sks speed (~2.00 GCD tier and lower) which are probably better off freestyling because you start to use a lot of filler then, which will really detract from your DPS. That potentially causes a slew of other problems, such as Higanbana possibly falling off or having to delay Tsubame, neither of which is desireable.