Good points, but remember that the earliest Sybok versions had him carrying off a bloody attack, not a casualty-free one, and THEN they started turning him into less of a Khan-type.
As for the laughing ... If they'd cast Max Von Sydow as Sybok (which I think was an early intention), I think he'd have put across the oddness of a vulcan laugh (he can make almost anything effortless, but if you look at his King in CONAN, when that guy laughs it rings false, though that may be the work ethic faltering under the size of the paycheck.)
Klaus Maria Brandauer was I believe another early choice, and while he is awesome in MEPHISTO and keeps NEVER SAY NEVER from disintegrating completely, I don't know that his dimensions would have put across a Vulcan (a Luckinbill problem as well.)
Luckinbill has one moment that works for me (it is the key one) ... when Kirk calls him mad and he reflects a moment ... luckinbill really channels Sean Connery there, and it is unfortunate in a way because it always makes me see how it could have worked with Connery, because Connery is a good actor with star charisma, whereas Luckinbill is a good actor without it, playing onscreen against western world icons.