In addition to damage stuffs, Dark Knight sub would provide a multipurpose wyvern. There's never been a sub-job for Dragoon that provided substantial damage buffs and a multipurpose wyvern before.

Stone I will also only take .5 seconds to cast, and provide a very small amount of TP, if all the planned changes come through. So, the vital act of not dying won't interfere with the vital act of hitting stuff with stuff that much.

Given, this is all very situational and hard to look at on paper, but it seems like a decent boost in utility. The ability to heal itself over and over might also make Souleater viable for Dragoon in situations other jobs probably wouldn't want to use it?