Infused weapon (and perhaps other passives, I have yet to advance far enough to test them) is not conferring a damage bonus to elemental melee skills. I tested with both manastrike and flame reave, and my DPS numbers are identical both on tooltip and the practice dummy before and after allocating skill points to the passive.
Edit: ran into the same issue with the passive that adds dexterity and elemental damage to elemental skills. I added one skill point into a passive that buffs intelligence and no other damage stats, checked the DPS tooltips, and then re-specced into the dexterity/damage passive. The resulting numbers were the same for manastrike, which scales on both dex/int. The expectation would be higher dps from the dex/damage passive as opposed to the int passive, but this was not the case.