Maybe the reason why it seems as though it hurts when we or another sundered person has an echo vision is because we're sundered? Remember we're experiencing a memory of someone or of a moment in time. Exactly how said person experienced it or the overall emotion those seen in the vision had if it's one triggered from a place. At least that's what I'm guessing when it comes to the second way we get echo visions. The only time we know an unsundered sharing a vision with us that I can recall is when we see the conversation Hermes has with Meteion after sending the other Meteia out into space. Of course we don't see if it hurts Venat due to her having told us to close our eyes. I do hope that the WoL starts to have a better time controlling it, but I have my doubts we'll see any improvement.