Intense flames could potentially have more crowd control. Though I'm not entirely sure. Thoughts?

Character specializes in all three elements of destructive magics, though only have 2 perks to use towards their "Effects". Disintegration is a no brainer

I didn't choose intense flames simply because I didn't want to chase down enemies. If I wanna chase something, I go deer hunting. Besides, with flames causing damage after the strike, I don't see it getting enough use to justify the perk point. However, if you've perked your Illusion tree at all, Aspect of Terror adds to your fire spell damage - that might be an alternative.

Disintegrate leaves little ash piles everywhere which, AFAIK, never clean up, meaning they'll be in your game forever (unlike regular corpses). I don't think Beth has fixed this one yet?

I haven't perked frost damage, but Deep Freeze sounds like a fun thing to aim for (eventually).

Aspect of Terror adds to fire spells without taking Intense Flames. (and if its taken before augmented flames it adds 15)

Yes they have actually, so long as the corpse isn't permanent to begin with.
ie: if the Corpse would have remained indefinitely so will the ash pile. But other ash piles will fade, more or less the moment you leave the cell.

Intense flames is worthless, the fear effect is the worst thing you want in a dungeon and it doesn't actually work on high level enemies.

Disintegrate is obviously useful, and deep freeze is also worth a perk IMO. Both of those perks work brilliantly on my character, who uses melee as well as destruction, the frost/lightning cloaks have the perk effects so disintegrate and paralyse enemies nearby under 20% health.

Ah, good to know... I have come across old ash piles long after the cell reset, so I didn't think it was actually fixed (this was in a new game after the last patch). Now I know why. Thanks!

(...runs off to perk destruction one more time!)

Yea probably this. Anyway i find all of the 3 "magic finisher" perks rather useless, if im not wrong it procs at 10% health or something. Why the heck would i want a monster to disintegrate when i've already taken away 90% of its health?

I decided not to use Intense Flames, Deep Freeze, or Disintegrate on my mage. I'm using the perks on other trees. I just have augmented flames out of 3 elements. So far I don't feel too weak because I don't have the others.

I stayed away from any of the final elemental Perks. I did Augment Flames, and Augment electricity (can't think of the actual names right now), and put two Perks into each of those. But as far as Disintegrate, Intense Flames, or Deep Freeze, none of them really appealed to me.

I thought about Deep Freeze, but since it only takes place when an opponent has around 10% of Health left, what good does it do me to paralyze them? If I just hit them one more time, they're dead anyway. That's like paralyzing them, but better.

Right. It seems to me that those perks are for visual entertainment purposes only. They don't actually do any extra damage. They just give you a visual effect you wouldn't get otherwise. And as someone already pointed out, the fire perk in question will likely do more harm than good. I'd rather have a dead enemy in front of me than one with low health waiting behind a corner up ahead.

Exactly. I don't want to take the time wearing down a particularly tough enemy just to have him run away in a flaming ball of panic... then I have to chase them.

Nobody like that...