One thing to consider (and there might be a RAW answer that I just don't recall at the moment): Is a spell that does damage or requires a save, but does not have an attack roll, an attack?
That could change how good it is or isn't for spellcasters.

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But, all in all, I don't think it'd be much abusable. Some, yeah maybe, in that you can make a build that avoids making attacks. But the boost from small size isn't itself game-breaking; even the stuff it could boost awesomely sounds fair to be awesome out without being really overpowered. Even adding to an optimized spellcaster wouldn't be a major boost (since what they already have, and it'd presumably mean not picking a race that boosts their spellcasting stat.)