After careful testing, we can conclude:
Keeping in mind that you can have 6 frames (100 ms ping / 16.666666666666667 ms intervals for screen refresh, for a monitor at 60 fps) of latency behind the server while still qualifying for 4 bars, thus it sucks to have anything less than 4 in pvp.
I find people with lower latency tend to just quick slot faster than you if they're lower latency, when there becomes a war of fast weapon switching. Oh and my fav is when people kill you before the flourish animations start. I've noticed the initial flourish animation starts to become less viewable at the end of a four bar to three bar connection. Often all they need is that first hit though, because of how the game blocks your own attack if they shield cancel flourish your face fast enough.
Now you're talking input lag, which is a different thing.
The flourish animation is no more than that: an animation.
The actual hit is an area of effect, so the flourish doesn't have to be visually where you are.
I mean, if you have a certain latency, someone can kill you before you see their start of attack and weapon switch. The server will register their kill before any packets on their attack reach you. Much troll.
The weapon switch discussion was on server latency, not input on client latency. Usually people rotate between a gf, flourish, or valiance while watching the other person's weapons. If you have less lag than them then you can usually boss them by switching to the proper weapon before they see it.
Currently I moved back to a house for summer and noticed how big of a deal connection latency is. I had 4 bars before I moved and after, but now it touches 3 bars and I can confirm it really screws with timing. I'd say even though it's a half a bar difference, I could be easily experiencing 80 more milliseconds, which I guess is enough to throw me off when things require right timing within a frame or two.
"So you could have a technical '4bar' while actually being between 3 and 4."
That is exactly minus 15 milliseconds drift allowed into the better bar range before it triggers. This means you need to have 84 ms lag to get back your 4 bars if you had 3 bars. In other words, it's 15 milliseconds harder to get the bars "promoted" than "demoted"
This has been on the forums for a long, long time. GMs posted it.
GMs also explained how they use some form of hysteresis to keep it from changing every 2 seconds.
So you could have a technical '4bar' while actually being between 3 and 4.
Also, I have to disagree. A 3 bar connection is still fine, 2 is difficult, 1 means you should not expect to be competitive.