So, your Vision of Confluence is a year 1 weapon. By using the respective ascendant materials, the highest you can bring this attack level up is 170. That is the maximum attack value for all year 1 Legendary and Exotic weapons (minus a few small exceptions). If you weren't aware, we're in year 2 now. With the introduction of Destiny: The Taken King, Destiny 2.0 persay, we've been given a brand new arsenal to use. These include all sorts of new weapons of all types of rarity, and the maximum year 2 attack level as of now is 320. So would upgrading your VoC be worthwhile? Not quite. It depends on what type of player you are and what weapon means to you. You can still use it effectively in year 1 activities like Vault of Glass, PoE, etc. Though in the Taken King, you'll need to expand your weaponry. To learn more about The Taken King, see here: https://www.bungie.net/en/pub/thetakenking