arcane blast ?...

Trying to increase our RDPS here not just free up debuff slots

Arcane blast does in fact do good dps, and freeing up a curse slot for a dps curse is also a dps boost.

We have hit the debuff limit a few times as well, especially on certain bosses such as brutallus, where we are max-debuffing him with everything at our disposal. Running even 1 extra shadowpriest or affliction lock can add quite a few debuffs very quickly.