Here's a quick way to raise your vitality. Near the Western Thalmont Node (which is the second place you meet Kira), you can find a location called Ram's Cave. Inside the cave you can find ten Thuloks, four Demons, and six or more treasure chests. The chests have some loot for you to grab, but the real interest is in the ten Headless Hearts from the Thuloks you kill, which will net you 74 vitality each (if your alchemy is at level ten or higher).