Cloud spells cancelling each other

[Unmouseable]

Not sure if it's a bug or intended, but I just got the Sphere of Destruction spell on my rogue and made a macro to cast it, Noxious cloud, and finally Power Blast.

I use a Noxious Cloud/Power Blast one already. The fire to kill is triggered from power blast so cloud only goes off the first time you press the key. Works very well if I do say so myself @.0

The problem I'm having, is after Sphere of Destruction goes off and does 1 tick of damage, noxious cloud is cast and Sphere of Destruction disappears.

I tried the spells by themselves, and it appears only 1 can be active at a time.

Oh, well I'm here I might as well ask if the failure rate for sphere might be a little high. I have almost maxed int and 50 in astral and my failure is still 20%, seems really high for the damage it does.

Well thanks in advance, and sorry if I ramble a bit

[PowerWyrm]

Not a bug I think. You can only have one active cloud at a time.