I used this spell on myself tonight, and lost some % in the spell for using an offensive spell on myself. However it did do what I wanted, by getting rid of the calcify I had put on myself. Can we make it so this spell does not sap the caster's % by casting it on themselves please?

Logically, it makes sense if you want to rid that calcification on yourself... Probably everybody does this ~once~ ??.

Use cancellation.

I used, for example, mass slow on my group, and it isn't hard to guess that I meant to. Nevertheless I still lost percents. I believe imms did not want to change that when I reported it.

I presume that you will need to use cancellation to get rid of decalcify, with the drawbacks that it entails. That's probably by design.