Riot, how do these dash mechanics work?

So, I've been playing quite a bit after a month or so, so I may have missed a patch or two, but I have to ask a question...

Does Veigar's wall still stop dashes? Because it only seems to stop them when it wants to.

Let me explain.

So, many games go by, and I'm able to stop some people from getting away or coming over and destroying me. However, sometimes, these champions have mechanics that make my wall not work for some reason. I'm not talking about Katarina's Shunpo, Zed's Shadow teleport, or LB's Distortion, I'm talking about how Ekko seems to be able to tuck and roll underneath my Event Horizon, and I'm not talking about the teleport after, he seems to just be able to roll out of the cage, away from me sometimes.

I swear, sometimes, I see Yasuo dash right through it, and sometimes he makes it through. Now, I know it's already trumped by Fizz's bullshit troll poll, because Veigar is already fucked in a match against this guy, so we might as well make him completely worthless at this point.

And also, is Vi's Vault Breaker a dash or not!? I can't seem to find any source that tells me otherwise, and she seems to just be able to launch her Vault breaker through some terrain, past my wall, and then murder me under my tower. I know for certain she can do this; she didn't dash before it was up or near the end of it, right in the middle of the couple seconds that my Event Horizon was up, she just ran right through it, one fist out, and then pummeled me into the ground. If this is intended, I'll shut up about it, but if not I'll try to get footage of VI just going through my e like it's nothing, and submit a bug report.