I agree that DRK's OGCDs are completely backloaded and need to be spread out a bit more to make it more interesting, I don't think moving more things into the 1 minute window is the answer.
You'd just go from an awful 2 min burst to every delirium being miserable.
Salted Earth is 2 OGCDs, Living Shadow is 1 (although you use that before bloodspillers), Shadowbringer being 30 seconds would mean you have to use it there too- Add that to the two Plunges, CnS and Edge spam, you go from not being able to mitigate at 2 min burst to not being able to mitigate for like, 12~15 seconds of every minute- that's like... a quarter of the fight? that you can't do your job during. (I'm not very clever so correct me if I'm wrong)
They definitely need to do something with OGCDs though, I still don't like Salted Earth and I think they should just give it's puddle to Abyssal Drain and then put a DoT on CnS that does the same damage as you'd get from the full duration of the puddle. I know that Archwizard said that the devs don't like DoTs, but that's essentially what Salted Earth is anyway, as well as Living Shadow. They're just more annoying to use than regular DoTs.
I'd also say that if anything they need to make Shadowbringer LESS frequent and more impactful, it absolutely doesn't feel like a capstone ability as it is now- compare it to Primal Rend, Blade of Valor. They're both something different, Rend is an AoE gap closer. Valor is a full ranged combo, although Paladin already had a lot of ranged stuff and I haven't actually played it so I can't say a lot.
Oblation is oblation, 10% DR is not bad but it's not... good, either. I think merging it with Dark Mind might be the wrong answer but getting rid of it and buffing TBN somehow is probably a good idea.
I think a second combo finisher would vastly improve the downtime, I haven't put any thought into this so I'm sure there's glaring flaws in it, but something like replace Syphon Strike with Spinning Slash, and then bring back old Delirium or something as a finisher that gives MP, while keeping Souleater as the higher damage HP restoring finisher.
I am aware that it'd be likely people would just spam the fuck out of the MP combo to get more Edges for more damage or whatever, but I'm sure they could fuck around with potencies to make the MP finisher low enough that it's not worth spamming it over Souleater- although you'd still need to get Blood from Souleater so maybe that's not really a concern.
My intention is that you'd have to actually be careful with your MP spending and plan ahead with what combo you're going to do. MP finisher would probably need to restore more than 600mp though, since it's not the 2nd action in your only combo like Syphon Strike is rn.