Have you played some variety of other 5ers? There's hardly anything you can do past a certain point if you're banging it. I mean, if you "consistently" bang all strings the low B might "overreact" compared to other strings. I do bang my strings with a pick (soft pick, alla' Nolly -Periphery-). That requires copious amounts of compression. Mostly to tame the low B string, which many overdrive/preamps will still have a hard time taming in the first place.
I too have a heavy hand for fingerstyle (and use a cleaner sound). Over time, I've developed an automation to pluck the low B string closer to the bridge when using the neck/P pickup only. It both reduces waves' amplitude AND provides more articulation, a clearer note (VERY welcome if you're only capturing vibration at such spot). I tend to go with the balance in other combinations and don't move (except for the ocasional note I want to fatten/lighten), just do this low B displacement without thinking when going neck/P soloed, I just feel the bass asks for it. I definitely don't like playing the low B over the P pickup solo unless it's real soft, deep but soft attack. You can probably wreak havoc with the B string on any bass.
Not saying there can't be anything wrong with your bass, it clearly is when it's so noticeable to you, just sharing some extra tips, even for any properly working 5er.