This happened to me and I agree it’s frustrating. But I think what happened is, in order to see the place that you wanted them to teleport to, they had to move slightly. Same as characters have to move to cast a spell where the player wants them to. And so moving slightly, they provoke the opportunity attack. So personally, I’m not sure that an opportunity attack happening on Misty step is the problem. I think the problem is that sometimes you don’t directly teleport, but you move slightly to see the spot where you want to teleport, and that’s what makes them hit you. Not sure how that would be fixed. Not sure if the little red sword icon shows up when you’re about to use Misty step, but it would be helpful if they would in those cases.