Level 1: Prefer regeneration overall. On some maps, you an can stack over 40 stacks and it can help a lot to get back into combat. It also helps you to revive faster.
Level 4: Resist is always a good thing. With Wraith Walk and this talent you can bait a lot of damages.
Level 7: Helps with fast and moving ennemies. Often but not always relevant, depend on the foes.
Level 10: This way I am going to survive more time and be a biggest threat. Though, the other ult is pretty good in a lot of situation. Take a decision upon the map, your allies and the foes.
Level 13: Add presence in long fights. Prefer Spell Shield in quick bursty engages, and sometimes another talent can be relevant.
Level 16: Double the slow. Consider Imosing Presence sometimes, depending on foes.
Level 20: All talents at this level are goods. Depending on your situation, choose one.