Finish off Virulent Paralysis - It'll never cease to be fun and you'll lose count on how many times it saved your life within the first couple weeks of maxing it out, especially if you solo tough content.
Combat Agility/Lightning Reflexes - Again, you'll lose count of how many times it'll save your life
Ancestral Guard - Instant click Group HoT. Enough said

Start on your Healing Adepts - It'll really help you fill a roll as healer in groups
Honourable mentions would be Spirit Channeling and Gift of Mana. But I'd recommend concentrating on working on the others first.