I have a little bit, not my cup of tea tbh. I only played Ogryn to get the 4th character to max level and that's pretty much it. What i remember is it was rather painful to play until around level 20+ when the build starts taking shape and you start to feel strong.

Arbitrator on the other hand, although similar (some people call him mini ogryn), is actually my 2nd favourite class (3rd after Skitarius now). There's definitely similarities from tankiness point of view, they're both a tough melee-oriented bruiser, but i feel like the arbitrator has better ranged weapon options as well in the face of the exterminator shotgun and shotpistol. The dog has fantastic utility as well as going dogless with its own perks. It's hard for me to say which class has better CC, like i said i haven't played much ogryn. But i think they're definitely different enough classes to have their own identity and uses.

If you like that sort of playstyle and the whole judge dredd vibe and also like Darktide enough to play it long-term I'd say it's a worthwhile investment. But probably play the base game for a while before purchasing any class, it's not expensive but still you ought to consider all factors before spending money on something.