Would allowing BLM to cast while moving break the job?

[Odett]

Knowing when to move and what skills to use beforehand is arguably what separates a decent BLM from a good BLM. BLMs may have a simple rotation, but we have to know the right time to use certain skills. You can open up with Thunder III by measuring the tank's running speed to the boss and have a long cast spell be used as an opener. On the other hand, using T3 instead of T2 for the rest of the fight would be inefficient, and in rare cases T2 as well. There are cases like In Titan EX where you'd rather get in a Thunder 1 because you know your Thunder 2 will be interrupted due to having to move very soon. There are also skills you can use to bypass having to move, like Manawall for landslides. When you're on the move, always use Scathe.

When you're a BLM, you'll notice that your DPS will be in its worst stage when learning a fight, as you're not sure what's coming next, but once you learn to anticipate things, your DPS will skyrocket once again. Use Sprint to get out and in as fast as possible, and using Procs while on the move is also a good idea, but don't let them sit there for a long time either. I personally like saving my SC for a ~500mp Flare and quickly Transposing for an instant surge of Umbral Ice, but if you know that the time you'll have to use up casting a long Fire 3 will get in the way of a mechanic, then don't do so. BLM is all about thinking ahead.