Mass curse currently does not interrupt the spell casting process like its 1st circle counter-parts do (individual debuffs). Mass curse should interrupt anyone caught in the radius of the spell just as all the other AoE spells currently function (eq + ms/cl).
Hello Isabel and welcome to Renaissance! It would appear you are new here, so a few mistakes are bound to happen. I believe what you're looking for is the Bug Reports sub-forum. While posting there may not get the attention of many players, I assure you staff does pay attention and will address your concerns according to the shard's design standards in as timely a fashion as they can manage. Good find and I hope the issue is resolved post haste.