I will check out Espgaluda, sounds interesting. The bar right now depletes every tick but gets a chunk back when you combo 10 hits and since most guns have quick fire rate (or for instance the shotgun that shoots 4 pellets) it will trigger quite often. Shooting enemies while in normal mode refills the bar normally.
In your opinion you actually want the opposite? The bar should empty out quicker so you're forced to be out of slow motion?