you are right - I am quite critical (and I am vocal about it, too)
Note:
Yes, if you use a staff, you should be able to do all that (use it as a melee-weapon, channel stuff through it etc.), but if you don't have one (or don't want to use it...) you still should have an auto-attack (magic is not dependent on a focus in DA - lucky them), I'd hate being disarmed and not being able to reach my magic...even more as a mage who normally does not have formal combat-training...so you would be useless without it...hand to hand is not something that works well without any training 
greetings LAX
You are correct, my good sir!
I would think being disarmed would be a bad thing for anyone, though
Video game mechanics aside, being disarmed usually results in being dead 
In the case of a mage being disarmed, they can fall back to their magic -- but if a mage is close enough to their enemy to BE disarmed, chances are they're getting a sword or shield to the face right afterwards to stun/kill them before they can get off a spell.
That's kind of the reason I loved DA2's mage melee attack. Enemy to close? Staff smack. There's no time to conjure up a spell if you're about to take a sword to the face. Better to use the solid piece of metal/wood to stun the guy attempting to stab you at close range, and THEN electrocute them or set them on fire.
On a "realistic" level, I would dare to say Circle mages aren't trained in attacking with their staves quite the way a well trained apostate or dalish mage would be. So some folks, like Vivienne, would probably have a backup dagger in case something like being disarmed were to happen. But I could very clearly see Dorian and Solas being able to Staff Twirl with the best of them. Disarming someone isn't exactly an easy thing to do, even less so if you're being smacked in the face by a big stick. 
As for our PC being able to use other weapons, there would be zero need for a handblast auto attack. If you've got a sword, your auto attack should be stabbing(or.. well.. slashing) with a sword. Otherwise you stand back and cast.
So yeah, I can't really ever see hand-blasts as auto attacks. Either you're casting spells, or you're using the enchantment within the staff to shoot projectiles, or you're hitting them physically (be it with the staff, or with another equipped weapon).
Hedge mages on the other hand, as we've been told, manifest their magic differently then those trained by circles or in Dalish clans. Which leads to all sorts of shiny new ways for auto attacks to manifest! Maybe their magic manifested as a type of aura that calms their enemies, making it much easier to sneak up and dagger them in the chest! Maybe they learned to focus their magic through their hands only, resulting in hand-blasts as their only means of projecting their magic at all. Maybe they "enchant" their hands and just "auto attack" via punching people in the face with flames on their hands! What I wouldn't give for a super strong and agile unarmed battle mage who can monk-style attack with bare hands and feet... unf...
*fans self* I.. I just really want to see more hedge mages...