I can understand the concept for people who are hoping to specialize in or focus entirely on Destruction. The point is rather moot though for people actually wielding full, proper Mages that use all at their disposal.
I myself never expected to win just using Destruction spells. I don't think a Warrior expects to win with just One handed either. Fact is, any class needs something else to augment their capacity.
Conjuration is a big help yes. But I also have a companion. Let me tell you, summoning two summons to aid my friend while laying down glyphs and calling blizzards and thunderstorms is by far the most fun thing I've ever done in a game.
So far no mob has made it past my three friends and two expert spells. Even if they do I carry a few daggers to whip out, although I svck with them they have saved me a few times.
For bosses, well, they are bosses. Takes some experimenting and a little luck. I don't have to launch "cottonballs" at them. If you are using novice level spells get out of here, you have no say.
By now the only spells you should be using are expert ones. If you don't have to time to cast them then make the time. You are a mage and not supposed to be the focus of the enemy. Either shout, gain some distance, wait until your companion recovers or summon a new set of creatures. It's all very simple really.
People are running around complaining that the fireball they learned eons ago that any new mage can cast won't work on a boss. There's a reason they are novice level spells. Use your expert ones and cause some damage. It's not hard at all for me to survive.