You're also noticing a smaller weapon damage increase across the tier.

Simply put, Monk I95 = 47 WD. I115 = 53 WD. Difference = 6 WD or 12.7% MORE.
BLM I95 = 71 WD. I115 = 77 WD. Difference = 6 WD but 8.45% more, which is magically LESS than the boost that non-caster dps get.

Though that does seem to be the primary outlier. Str/Dex/Int all end up in the same ballpark, I believe, somewhere in the mid 500s. But WD, which is the single largest contributor to anyone dps, goes up by a smaller % value for casters.
Now if the I115 caster weapons came with 80 WD, then things might look a little better.