Look, the answer is almost always “it depends on what you have,” but I personally find Phenexa-Ludwig-Alfrike or even Phenexa-Ludwig-Proteus way, way too useful against many event bosses, and Ludwig-plus-other-Slow-hero useful for “use two Slow Specials” PoG tasks and Rush wars/tourneys.
Also, Ludwig is still just my best Taunt hero (and auto-Taunt due to LB2).
But that’s all me. If none of those things matter or help you compared to your existing roster…
…look, I understand the challenge. Rationally, I should tear down my old non-costume Gravemaker, but he’s like my first non-vanilla 5*.
Unlike GM, though, Ludwig makes the monsters around him… better, and that makes him more potentially valuable than most any hero of even around his age. That makes him tough to tear down, since he can —at least in principle— always work together with even future heroes as well.
Put another way, it was hardly unreasonable three years ago for Old Cynic to write
so that we are now seeing a serious thread of “should I strip Ludwig and basically stop using him” says a lot about the direction of the game since.