Fedifensor
Explorer
Well, the build is meant to be playable...I just consider the AC more important than you do.
* +5 HP on a character that already has 159 HP is trivial.
* Two extra healing surges (since 18+5=23) are useful...if you're taking enough damage to use those surges. This build is designed to minimize incoming damage.
* +2 Fortitude (again, 18+5=23) IS useful, which is why I've been considering whether Wisdom or Charisma can be lowered in the build. Wisdom is my top candidate, but I don't like losing the Spell Accuracy and the push capability (if I switch to Thunderwave).
* +2 on Staff Mastery (which comes into play once per round) is useful, but possibly overkill given the build's current defenses. A natural 20 always hits, after all.
Nice, but not overwhelming...especially when the higher levels rely on encounter and daily powers for the majority of damage output.
The build already has Toughness, and there are a few feats that could be dropped if the player wants access to other feats. For example, while Solid Sound is a nice defense boost, it is situational and can be removed if necessary. Epic Resurgence is nice, but depends on you rolling a 20, making the effect unpredictable (and you have Spiral Tower Action if you really need another encounter power). Arcane Mastery is nice, but if you prefer to use action points for an extra action (since you can only spend one per encounter) then it may not get much use. Finally, if you lower Wisdom, you may as well drop Spell Accuracy.
Which is still significantly less often than a weapon user, who always uses the same weapon to attack. Trying to build around a single damage type generally means you have subpar choices in your power selection. It can be worthwhile for cold mages (due to Wintertouched and Lasting Frost), but otherwise I wouldn't recommend it.
One of the purposes of the build is to allow you to be a hot target. The defenders can spend less time worrying about you and more time worrying about other characters (such as the strikers and leaders). The build also has a good Reflex save, which helps against attacks like breath weapons (the game is called Dungeons and Dragons, after all).
Oh, it's certainly not the only good staff build. It really depends on what you're looking for in a character.
