Depends, what exactly are you doing? If your goal is for maximum damage, then spamming CDC is what you want to do. Casting damage spells delay's your attack rounds and reduces your TP gain rate.

And lol at HS doing 1500 average, unless your not counting the 0's from it missing. A.Spikes is a SC spell, it's DMG:MP ratio is bad, but all of the big number spells are bad MP ratio's. What your looking for isn't DMG:MP since that's a bunch of BS, your looking for DMG:Time ratios. How much damage are you doing for the period of time you spend casting. Even at low MP you can still TP / WS and CDC will beat all our spells that don't have CA + Efflux on them. This is why a damage orientated BLU should be /WAR with DWIII + TA set and not /RDM with Mag. Acc swords.