Increase what? Haste? It's meant to only give 1% haste per spell cast in Incarnation if that's what you're referring to. If you're talking about the increase to dmg, then no i haven't felt anything odd.
the damage increase, not haste. the haste increase is a result of an artifact trait. i am talking about the damage increase of the base talent. 35%. a number of tests have returned as around the 28-28.8% mark.
Well, it's easy to test since our spells are almost all fixed damage, and i haven't been able to reproduce your discrepancy on Moonfire, SW, LS and SS. All were within 1 damage of 35% damage increase with Incarnation active.
You sure you didn't miss some temporary buff during your tests?