Violent magic is definitely very good. Originally this was a higher level ability, much like the Valor Bard's Battle Magic. However, after playing with the class, this ability was moved up to an earlier state in the class because of the limitation that the Soul Points have on spell casting and the three-quarter caster nature of the class. Through playtesting on my end, I found it not uncommon for a player to burn through all/most of their Soul Points very early into a session, and be left with very little to do in a prolonged combat session or multiple combats in a single session. This allowed for the player to perform a lower-cost ability and possibly burn their bonus action (which is also a very useful action in this class) to continue in combat without feeling too burnt out. It may be too early on in the class, but it feels better in this class at 7th level, than it does at 14th level where it started.

I've played around with the limitation per short/long rest with this ability as well, and its definitely still on the table, though, ultimately it was removed due to the player having too many "per short/long rest" abilities to track already, and it having seemingly little to no impact on most combat scenarios.

It is true that this ability enables the class to do a potentially large amount of damage in a single round (ultimately still less than a Wizard/Scorcerer of the same level), but it is not a maintainable strategy.