Hey dancook, out of curiosity... have you tried Plague of Toads - Rain of Toads instead of Acid Cloud? The LoH coefficient for it is much higher than Acid Cloud. There is no up front damage but the ticks hit MUCH harder than Acid Cloud, and the effect stacks for repeated casts in the same area. It is also a fraction of the mana.

I would be interested in seeing a video fo you testing it out, curious if the lack of the 24 yard area of the Acid Cloud rune causes issues with using Rain of Toads.