Thunderbolt does 5 damage. It is the strongest unconditional single-target CC spell. If you're thinking of Thunderstorm, that was never a problem. Firstly, users of pump spells get over 10 quanta easily in time to kill this since it's insanely expensive as an attacker and takes a turn to use its ability (which costs as much as upped Quint). That extra turn isn't needed per se, but it's there. Shockwave, Rage Pot, Lightning.. all the most used CC spells kill it, and so does Elite Oty. Only scenario I see it helping is against Owl's Eye, and that's if they're not flying them and only have one out.
The change is aesthetic to me.