It improves force barrier. Thats the overshield you get for melee killing someone. Ward of dawn is the bubble so no you cant have your bubble up constantly. The specific upgrade on it increases the duration of force barrier, not ward of dawn. And the other upgrades are increase reload speed with special weapons and increase melee attack speed

Well -blam!- me then....

Yeah xD I thought it was gunna do some crazy shit for ward of dawn as well and then i got it from the nightfall and was promptly disappointed :p