Great... you can make Flames and Sparks 25% more powerful at destruction level 30, and then add another +25% more powerful at destruction level 70. But Firebolt and Lightning Bolt both out put damage quicker then Flames and Sparks and both have a better damage:magicka ratio.
Base spells with no perks:
flames 8:13 = 61%, Firebolt 25:36 = 69%, Incinerate 60:262 = 22% (this is why mages complain destruction is broken, this ratio is DREADFUL!)
with 50% damage bonus and 50% cost reduction...
flames 12:6 = 200%, 37.5:13 = 212% 90:131 = 69% (yeah incinerate has far to great a magicka cost, you pay 3 times the magicka to kill a mob in just under half the time of firebolt, missing the spell WILL hurt)
The only advantage Flames and Sparks have over the apprentice spells is that flames and sparks can hit more then 1 enemy at time, since they're small cone AoE attacks but this means you have to be almost in melee of two enemy which is the place a mage is vulnerable at and should be avoided. Just incase you do not get the figures above, the higher the percentage the better! The apprentice spells effectively have the best straight up Damage to Magicka cost ratio in the entire game.
Just so you're aware, the Illusion perk Aspect of Terror adds 10 DPS to your Flames spell. Mine currently does 18 DPS without any perks in Destruction - presumably it'll raise to 27 eventually, once I get the 50% Fire damage perks. It's probably a glitch but it's still pretty handy, it makes Flames extremely powerful, and I'm currently level 18 with my Dark Elf Illusion/Conjuration mage. It'll most likely still be weak by high level though.
As for Illusion, I think you're playing it wrong. It can be extremely powerful if you use it in conjunction with Sneak (to be honest you'd be foolish not to - obviously the spell is useless if you're already in one-on-one combat with a foe). Dual wielding "http://www.uesp.net/wiki/Skyrim:Illusion" the level your Illusion spells affect, and the doubling occurs AFTER the bonuses from Kindred mage (+10 levels), Animage (+8 levels) and/or Rage (+12 to Frenzy spells like Fury) are calculated.
Basically what that means is that a basic "up to level 6" Fury spell can have 22 levels added by perks against humans (or 20 against animals), which is then slightly more than doubled. In other words, perk Illusion enough and Fury will affect (6+12+10)*2.x = level 56 (or more - "slightly more" than doubled) humans. Which is above the level cap for enemies. Not bad for a Novice level spell which will cost about 10 mana (unenchanted) by the time your Illusion skill is 70, high enough to get the Rage perk!
Illusion is very strong, and Fury is a brilliant spell if used properly.
...however Destruction is still lame