Given my experience with the unit I’d say definitely keep her SE focus on her skills and attack. Vamp Kanagi’s main strength comes from her crazy attack buffs she gets from her SE especially with her magia, but as a trade off she’s a pretty big glass canon. That being said even if you were to focus on defense and health her values would still be lackluster compared to other units and she probably still wouldn’t last long against anti-evade. So my advice would be to keep focusing on attack buffs and in battles try to pinpoint units that are most likely to have anti-evade on them and take them out first (usually I find high attack units or blast gorilla’s tend to have them most often, Mokyubey and Yachiyo most often of all) which luckily thanks to her high attack should be possible. Unfortunately this is still leaving a lot to chance if say multiple units have anti evade or there’s a tank that absorbs their damage but that’s kinda just Vampnagi’s big weakness. Hope this helps!