I use this when I'm in groups on our MT. Since I play on Zek, I just remove one of my 3 consistantly loaded PvP dots (2 corruption and 1 magic-based: Splurt-line) and use the spell gem for this buff instead. It's added damage and although using a spell gem for Necrotic Ally would be much more damage, Necrotic Ally has too many issues being an AoE for me to think of using, but it is always in the back of my mind which I'd prefer.
Our aura(s) and totems I don't find very useful and don't ever use them, if not rarely