The point isn't to compare to warrior but to mage with attack spell use. You should look at it in this way. It' not because a warrior will perform better that a mage with attack spells will perform better.
About some of the points you bring, and only from a KBTL point of view:
- Against dragon with high magic res your attack spells will be ridiculous.
- You clearly didn't used a lot target with mage otherwise you would know that a mage could use against a big army of long range target + stoneskin + magic shield all along a fight and some other spells at same time. And when used on proper target the damages are ridiculous.
- It's for example on Archmage or dragons against plenty magic long range, on Cursed Ghost on plenty poison/physical long range, on Knights or even Horsemen against anything. A warrior will have much pain to do the same because it won't has the mana and more important spell duration will be too short. But more important in many fights, it's much much more efficient than using attack spells.
- Against less long range you could use target on the proper target but with few protection and use your other spells for some other options.
- Glot armor is very very far to be the same than trap, it doesn't make lost any movement points nor any special attack when a trap can. For the random factor your are partially right but not fully, for example dragons are the easiest to predict when you set them a temptation trap.
- You can use Time Back with mage too, less often but still at right points.
- Cursed Ghost is obviously to use with the Paladin skill that disable any morale penalty because of them. And not only a warrior can learn this Paladin skill but a mage can too.
- Black Hole use plenty rage and isn't something for a mage. Double armaggedon is only for a rare use and will make you suffer significant lost. It's weird to compare a mage by using such weird tactic that are a good choice only rarely.
- 12k Leadership more isn't right, that's depend when in the game and what items used.
And I agree that warrior seems better but not that this imply that mage is better by using attack spells in imposible mode.
EDIT: There's also an important disadvantage to focus on attack spells in impossible mode with a mage. That means that you'll focus on magic order or/and magic chaos level 3 first when mage distortion level 3 asap is a huge advantage. In my current game I even get it before level 2 for chaos and order.