I will admit that i have heard that HG is good for rags but i havent even seen that fight >.<
The dps added is pretty minor - phase 2 on the molten seed adds. It's not THAT much more damage. Hw glyph is better because it stuns them and stops raidwide damage.
Personally, I have 1 point in HG because I tried running without poj... And to be quite honest, I haven't missed it in the least. If you know where to be, when to be there, and when to move... Honestly the talent is meh for farm content. Nice little perk for learning though.