Time to revisit this topic again. You're probably asking yourself why we're talking about this again. Well, to be honest, it's because it's the end of an expansion cycle. While we're prepping for the next expansion that will shake up mechanics and stats, we find ourselves at a point of speculation -- and therefore, things like Telluric Currents find themselves back in the crosshairs, so to speak.
The talent itself is something you use, or you don't use. There are some hard facts about the talent. You do not need to stack hit to make it useful, only to make sure every bolt hits. It is not mana neutral, using the talent and casting Lightning Bolt will indeed fill up your mana bar. It can be used to supplement low spirit totals for beginning healers, and can be used in certain phases on raid bosses to maintain healing mana totals. Whether it is optional or mandatory depends on a lot of factors up to and including the team you're healing with and the content you're healing through.