So with the coming PTS patch Negate is gonna get a huge buff, that denies anybody from casting any magicka-based skills while standing inside it. From a performance perspective that's certainly better than the current version, which only removes some AOE's at a specific point in time without any continuous effect.
However, Negate is often cast in choke-points with lots of players in one location, but also big clusters around the point of interest. This means that while the players inside the AOE will not be able to cast any magicka-based skills, everybody else will still be able to place any AOE into the choke-point. As a comparison, let's look at the initial version of Negate, which was breakable, but prevented the placement of abilities within its AOE for the full duration. As a result, contested areas would be with fewer particle effects for a longer duration.
I know that the version on PTS right now is better for numbers, but I think that that giving some power to the few in turn for less ping isn't such a bad trade.