Their "fix" wasn't even a fix. It was an attempted workaround. The issue is still around, just slightly mitigated.
As far as we could tell, the issue stems from the rate of communication between client and server. The intervals between the servers updating everyone's 'official' location are longer than most people would like. For this reason, people are able to get 2/3/etc meters outside of an AoE on their screen before it hits and yet still receive damage from it. The server hasn't officially updated their position as outside the AoE radius, even though the client sees themselves outside of it.
Easy example to witness this: Try running around with the zerg FATE-farming crowd sometime. Watch the people around you. Notice how basically everyone zooms ahead a few steps, then falls back a few steps. You're all moving at the same speed, yet people are periodically moving faster or slower onscreen because of this delayed rate of server/client updating.
SE's "fix" to this had nothing to do with increasing the rate of communication between server and client. All they did was decrease the "size" of a character to a single dot in the character's center mass. This makes the player a smaller target to hit (and therefor slightly easier to get out of the AoE since they no longer need to worry about a foot or an arm still being in the AoE), but doesn't actually fix the core of the issue.