If I remember correctly, at current top-gear status, 15 INT will only be about 3~4% of your damage output. Suppose you do a whooping 300dps all the time, that's about less than 15dps difference. I'm not sure it's so game breaking to perform slightly lower.
With that said, I do think the SMN/SCH sharing physical bonus stat is just a programming flaw that got classified as a feature, like many things in software.