No, all damage is reflected back. People usually mention that you should only bother to defend yourself against reflected damage if you deal physical damage, because your own physical resistance is low, compared to the rest. But this is something I disagree with and I think any damage not taken, no matter how small, is welcome. Especially if your build aims to have the highest possible damage, which would mean that the damage reflected back is also proportional to it.
I agree and that’s why you have more peace of mind upgrading your reflected damage resistance. But in early game the crowds that have reflective enemies are usually smaller and you should make an extra effort to spot them and attack only when they have their aura down. Also, going as fast as possible for the constellations with reflected damage resistance would help (like Owl, Lotus or Crane).