Magicka isn't an issue, it never was and it never will be.
Mmmm... Interesting that you refuse to answer any of my questions... I will do it for you then.
All the above actions are free to do (substitute stave attacks by "weapon" normal attacks) for a stamina user. Free in the sense that they recharge stamina while doing them...
...That's the key concept. The issue is that ppl has got used to the "effective mana regen" triggered by the "mana freeze". That's why it's not strange that they think mana regen "doesn't matter in combat"... OFC it does not, because under common use it's 0. That's why they are forced to focus on just 1 trait... Mana discount.
Regarding the direct meaning of your phrase... Well, I just take it as "chest beating", because if you label something that lacking of prevents you to do anything as a Mage as "will never matter" is like saying that HP doesn't matter at all either.
As for your "accurate tests" they are certainly wrong. People have tested it with the developer console. Dual Casting does do more damage, about 25%, but loses roughly 33% Magicka to damage ratio. Infact it may even be 40% Magicka to damage ratio. I can't seem to find the post with the numbers.
That explains why my tests show it... If you spend your entire mana bar using dual casts firebolts compared to spamming a single firebolt, by the time your mana bar is spent you do slightly less damage by DUAL casting than by spamming (I attributed this to the slight mana recharges that happen between "spell arms", which are more often when single spamming). I used my Housecarl as target to check the final resulting HP to simmulate what happens on the real fight... When you chain spells and "translate" mana to damage.
Can you link me to the thread were they detail how to use the console to get numerical combat feedback? I'm not only interested in this but on checking wards and how physical weapon stats are translated to final damage...
...After my experience with Fallout 3 "console havoc" I even unbind the activation key to not accidentally type something I later regret.