heh ... i don't know for sure but how about flame strike/blizzard/meteor storm ? or maybe dispel,devour magic .... they can all target unit or point. Generaly spells that can target either unit or point are AoE spells.
I'd say go with channel. Look it up in the ability guide to get more information about it, if something still isn't working the way you want after that post here and we'll figure it out.
Shockwave, Carrion Swarm, Crushing Wave, pleh... they're all point-based targeting, it's just you can select units, but it will fire at the point when targeted, or at least that's how it worked when I used to use those abilities.
Just *possibly* keep that in mind.
If you could *somehow* dummy a strange version of attack ground, I don't see why it wouldn't work.