Why the heck do you give the half elf dilettante ability a value of "0" for everyone but fighter and rogue?!? (And no, "Because it suxxorz!!11!" is NOT an acceptable answer.

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Like the human's extra feat, there are suboptimal ways to use it, but there are also nearly always ways to get a respectable benefit from it. If you want to make the argument that it's not as good for specific classes, like wizard, fine, but for the most part, you can find powers using primary or secondary scores that will effectively match your class's encounter powers in usefulness, at least through heroic levels, and likely thereafter.
Take a Warlord; from what I've seen so far, my favorite pick-up would be the Priest's Shield. Why? It's a Strength based attack that grants a defensive bonus; it's a good candidate to replace Guarding Attack, even for an "inspiring" Warlord. "Nuh-uh," some may say, "It only does half the damage! It's half as good, like the half-elf!" They would be wrong. Look at them again. While Priest's Shield only does half the damage, it grants you (at least) twice the defense; Guarding Strike helps another character, against the target of the attack; Priest's Shield helps another character AND you against ALL attacks. Good for a Warlord who wants to stay up front to keep moving the defenders and strikers around/granting extra attacks. Even if you're playing the (likely rarer) "tactical" half-elf warlord, as long as you have a 12 or more in Cha, (and you're a half elf, so why wouldn't you?) it will still give you twice the defensive benefit you would get from Guarding Strike, and still against all attacks. That's one example; there are other good choices for nearly any character.