Fight Club: Build your own private arena for dueling against your friends. Or enemies.

PerArdua

Ok there Zos just spent an awful lot of time , crowns and gold building a duelling arena over the lake at the back of earthtear cavern . I have just found out that my time was wasted as ground based aoe skills and ults do not work . It says invalid placement or some such in the top right hand corner . It appears that the aoe is trying to cast on the lake floor not on the platform I built . I have tried wood planks and stone blocks but neither seem to have any effect on changing this .
Is this a bug or by design ?
I will summit a ticket when the account maint is over(logging in says I m logging from a new browser / device and not getting an auth email password but that's a whole different issue ) , but don't expect much more than the usual auto reply

@ZOS_GinaBruno @ZOS_JessicaFolsom @ZOS_KaiSchober