The whole repeated reasoning of "i can't see Storms doing anything, therefore they are useless" is moot.
It is like saying a manipulated 6-sided dice that has a 1 in 4 chance to land on the 6 isn't better than a regular one in a nice evening of D&D, because the human mind would not recognize this effect in action, without statistical analysis.
Sure some additional % tuning could be done, but the problem is that players would still not recognize the Storms benefits until it gets boosted enough to produce regular extra turns after explosions, at which point Storms would be way to impactful to just be low(no)manacost secondary effects.
Anyways, the storms may be too subtle to be considered worthwhile acticely gaming them by some people, and that might be a valid point, but that is why they are minor secondary effects to spells with virtually no relevant extra manacost.
I also don't think Suncrest is particularily weak, they have some really solid troops considering they only have their starting lineup of troops so far, i'd argue there are old kingdoms with less appealing troops, even if you completely disregard the Storms.