If RoL/Hope decks are really that annoying maybe try nerfing Hope? Maybe the problem doesn't lie in Fractal? Cause every other Fractal deck is alright to counter, but RoL/Hope is a lot harder? I find it funny that Light has untouchable permanents when even Aether doesn't have them.
I'm sure you've seen fractals before, they're a rough or fragmented geometric shape that can be split into parts, each of which is (at least approximately) a reduced-size copy of the whole (Mandelbrot Set being my favorite of them). They're usually never ending, or can be made so. Kinda like the golden number/ratio. Therefore, the unlimited copies is the nature of the Fractal card.
What kind of decks use Thunderstorm? Decks designed to counter Fractal decks. Like my Aether/Air deck, specially designed to shatter the defensive abilities of Hope with an overwhelming 198 Wyrm ^_^ Unfortunately I never get it that far *sign*. Anyways, people build decks with various strength and weaknesses. Strength of rush decks are that they can win real easily (not often with a perfect though) and their weakness is that they lack creature/permanent control. With my deck you know its strength, however that's also its weakness as I have to rely on that Wyrm to get that strong, or to draw a Thunderstorm eventually soon. Also, just cause you don't see anyone in T50 use them doesn't mean that no one uses them. The T50 are only 50 of the large population of the elements world. How would you control a RoL/Hope deck? Just like you would for any Army deck, just that Fractals make that army grow a lot faster sometimes.
A Pest/Fractal deck is good quanta lockdown, but it's lacking in damage. Unless you got a dragon to Fractal later =P However, Earthquake/Quicksand is just as deadly don't you agree? And that can be used in a Shrieker Rush Deck. A SoD/Miracle deck is even more annoying cause it just waits for you to deck out. Just add some creature control or some more healing and it'd be even better, and more annoying >_<
The term powerful is relative to the situation you're in. Powerful as in the creature's skill is really useful. Powerful as in the creature's stats are really high compared to its cost. Powerful as in this card is the card that can turn this whole game around and win it for you. <--- Usually that depends on what type of deck your deck is up against, and is situational. Against a creature control deck with no permanent then ... well even then Fractal isn't what's going to save my butt, my Immaterial creatures will do that for me. Miracle <--- Makes it go from "I'm going to win" into a repeat of what you just spent the last 5 turns doing. Hope <--- Complete shut out with sufficient RoLs on the field. Earthquake <--- Early game it prevents quanta production, and therefore stops your opponent from using any high costing cards (Also can stop duos dead in their tracks because some decks require the unison of both elements). Used at the right moments and these are killer, as are other cards. Other times they're just dead weight. Fractal <--- you don't draw the right creature/you have a full hand/not enough quanta. Miracle <--- you don't use it at 75 health, but somehow your opponent dishes out enough damage you completely take you out (This is fun when you're the one that does the dishing xD). Hope <--- All your RoL are lobotomized or killed in a large genocide. Earthquake ~ Try quanta-stalling a Pillarless/Towerless deck xD
Finally, this card lets the harmless monsters make a big comeback. I mean ... what use would RoL or Ball Lightning have if this card wasn't in the game? ... Cremation only? Before Fractal where would you see the use of Ball Lightning? Now I use it as a surprise overload of damage to finish off my opponents. It's neat and it's fun taking your opponents down with a Ball Lightning (Actually I use a Spark, I've been upgrading my other cards first before Spark, but it's coming soon ^_^).
Before saying this card is overpowered, take a good assessment of all the other cards in the game.