Considering master difficulty, what do you guys think about the damage of destruction's spells? In my opinion even the master spells have low damage. Have I made something wrong or they are really this way?

Nothing you did wrong. The general consensus is that it needs to scale with the Skill level. You can't tell how weak it is until you play on Adept or Master. All the damage on the spells are pretty much static.

Destruction this game seems to be pitched with using other schools along with it in mind. Weither that's a good thing or not is up for debate, but I wouldn't send a warrior into battle with only a sword and no armor.

Alone, destruction won't be enough to kill everything infront of you on higher difficulties. While I don't think that's a bad thing, I wouldn't be against a dlc revamping destruction to give it a bit more kick. Just keep it so mages should be inclined to use all schools. Specialization should be rewarded, but not a way that you only need one skill.

Destruction seems to get weaker as you level up. During the tutorial sequence, I do reasonable damage with it, but by late in the game, even characters I built as battlemages (focus on magic, back it up with melee) seem to function more as spellswords. About the only time they still use destruction is against dragons, because I svck at archery (none of my six characters uses it, though several tried).

My fix:

1. Eliminate the ability to spam destruction so that it has zero magicka cost (max it out at 80 or 85 percent reduction), then increase spell power as follows:
Apprentice - 1.5x
Adept - 2x
Expert - 2.5x
Master - 3x

2. Retain the ability to spam destruction's magicka cost down to zero and modify it as follows:
Apprentice - 1.2x
Adept - 1.4x
Expert - 1.6x
Master - 1.8x

In my opinion, to have profit of skyrim you can't be so pure, like a warrior that uses nothing beyond a sword or a archer that just uses bow. But in you guys opinion what would be a good partner to destruction?