As it stands, the Eldritch can use both AoE Str/Con and AoE Dex/Qui instant stat debuff spells at the same time. Spiritmasters for instance, with access to the same type of spells, have to wait 5 seconds after using one of these spells to re-cast either of them.
I believe the Spiritmaster mechanic to be the correct one, but I am not 100% sure. Someone more knowledgeable about this topic needs to confirm which mechanic is proper for the desired patch level.
Eldritch AoE Stat Debuffs do not share the same cooldown timer
Re: Eldritch AoE Stat Debuffs do not share the same cooldown timer
"but I am not 100% sure" = not a bug report. please do proper investigation