DRK's Blood Gauge bar does a reasonable job, in my opinion, of conveying the character's stance-state and Blackblood charge in a manner that can be evaluated quickly. That said, I think it could be improved by having a red version of the spikey effect displayed for Grit to indicate when Darkside is active. There's plenty of room in-between Grit's gui spikes to put red spikes for Darkside and creating the new gui element wouldn't be too hard since you could literally just use a color swapped version of the same element that's currently used to indicate Grit's status. Graphically this would also have the benefit of red/blue both being primary colors, so when both stances are active the alternating blue and red spikes should be easy to tell apart from each other for most players.