On its own its not bad but its setup to get really big requires time and some effort. Sol does 230 + 65% ap and "fires the core of a newborn star" That detonation should be a catastrophic event. My issues just how a quick Q then Break is the exact same as a Lane sized Q that's been growing.
Now Looking at some other Hard CC in an aoe. Antivia, Swain, Rakan, Annie, Zac, donger, Zyra All have hard CC abilitys that are comparable or superior in damage to Sol, yet none of them get as visually dramatic.
If sol Q just had a small effect on its growth, I would find the skill more rewarding. Something as simple as it now pulls enemy champion hit to the center. The lack of impact on its size to its effect, as well as the fact A big green goo blob landing on you deals higher damage just don't match my expectation.
His R as well, I grant you its an aoe with good range and the knock backs usefull but space dragon breath max level is only 50 damage higher then a Cannonball from
10 levels lower and she has better Ap scaling. Hell Braums R has the same base scaling, as well as being only 0.1 Ap lower scaling.
I'm ok with gameplay breaking logic and reason, its a game after all. Its not saying he is bad, just that I feel there is mismatch higher on his visuals to his ingame effects. Traditional damage > visual but Sol Visuals > damage