In my opinion, the Devour talent is useless at the moment.
Parasitism heals 1% of your health everytime your DoTs does a critical hit, that's like 130 points of health per hit in PvP.
Seriously?
Also, Devour increases 20% the amount of healing that Parasitism do, that's 1.20% of your life (156 points)
It's like wasting 2 skill points...
So I came to the conclusion that Devour need an upgrade, the next one:
Devour (Rank 1)
Your parasitism skill now extra heal 2% of your life.
Devour (Rank 2)
Your parasitism skill now extra heal 4% of your life.
Then Parasitism will heal 5% of your life, that's 650 points of your health, enough for me to stop complaining