There is little consensus that DRK is particularly button-bloated. It is the fewest buttons among the tanks. And "solving" that is as simple as in some way wrapping the effective total damage nullification Oblation into either TBN or Dark Mind (changed to be castable on others, perhaps by upgrading to that new "Oblation" form).
Or, as in the post directly above, by trimming the bloat from the Tank Role Actions. We do not need have Rampart siphon power away from our own native tools; we could instead just have a 2nd charge and a lower recast time on our core 60-90s defensives. We do not need separate buttons for Low Blow and Interject. We do not need Shirk. We would not even need our various names for "Tank Stance" if we merely buffed Provoke.
It's also not what makes our opener bloated. Salt and Darkness is not a different button from Salted Earth. The second cast of Shadowbringer is not a different cast from the first. Those 4 edges are not separate buttons. That's a matter of density/timing of casts. On which note...
For the... fifth(?) time now.
You take casts from where the density of casts is too much... and instead put it anywhere the density of casts is too little.
Attaching a MP cost to Shadowbringer and increasing MP generation by 3k MP/min already gives our 2-minute burst back 2 weave spaces. And it gives us 2 more Edges between each of our 2-minute bursts instead of us half-forgetting it exists during those lulls.
Attaching a MP cost to Salt and Darkness and increasing our MP generation by 2k/min gives our opener back 3 weave spaces. And it gives us 1.33 more Edges between each of our 2-minute bursts instead of us half-forgetting it exists during those lulls.
Attaching a MP cost to Carve and Spit / Abyssal Drain and increasing MP generation by 3k MP/min already gives our 2-minute burst back a weave space. And it gives us another Edge between each of our 2-minute bursts instead of us half-forgetting it exists during those lulls.
These each makes zero change to the job's APM. That APM is merely moved from where "There's too much!" to where "There's not enough!"
It is that simple.