Was revisiting my not-all-that successful first character, an attempt ata Battlemage whose perks are mostly Destruction with some in Light Armor, SMithing, Enchanting, and a handful in One-Handed Archery and Restoration. She's real all over the place and unfocused.

I was gonna re-roll a new mage but thought I'd give the first one a try, and after fighting some giants I realized the problem with her build. Having almost all of her perks into Destruction and almost none in the other magic schools (a single point in Resto to make Heal cheaper, and some perks in Enchanting, none of the other schools have even one perk) I think the problem with how I have built her is a lack of control. Chuck a couple fireballs then I am running around trying not to die until my magicka comes back.

So, curious about other mage players, what school of magic you prefer? I've read some guides that recommend Illusion or Conjuration as a character focus over Destruction, but I dunno how they handle dragons and bosses without Destro's raw firepower. Thoughts?

illusion+conjuration is devastating

destruction should be used as nothing more than a supporting class, if you're looking to maximise damage output

Illusion, Conjuration and alteration.

Conjuration is a good support skill for anyone willing to dabble in magic. Personally I find Destruction the most fun of all 5, nothing like blasting people to Timbucktu with lightning bolts and fireballs. But if you plan on using Archery, you won't really need Destruction, or vice versa. Honestly it depends on how much you're willing to invest into magicka boosts. My main uses the same exact skills you listed: 1H, Destruction, Light Armor, Resto, and the tradeskills. However Destruction and Conjuration can complement each other very well. However if you're making a pure mage, just use all of them.

"Best" is really subjective, as it is a matter of preference.

For me, Destruction is not the "best" school of magic, but that is because I don't prefer throwing fireballs at people's faces. So for my preferences, it would be Conjuration.

"Best" in terms of effectiveness? Well, just like any other skill in the game, when used properly, Destruction can be very effective. In my experiences with Destruction, it is both fun and effective.

But I enjoy chopping baddies up into bits with my dual wield swords too much to throw fireballs.

Illusion spells like Fury only work on enemies under level 6, if I recall. Even with the perk tree's level boosts, how long do they remain useable? Wouldn't they become powerless after a certain level?

the perks add a level boost to them, which isn't visible in the active effects i believe

also, you will get stronger illusion spells as you level up, it needs all the perks however to be fully effective

e.g: a dual cast of frenzy will work on mammoths and giants (level 50ish)

Destruction is better suited to a hybrid class like a Crusader or Spellsword. Something that can dish out consistent damage when the magicka is on regen. Pure mages should only use Destruction after they've got their summons in play, followers buffed, and enemies paralyzed/pacified/frenzied.