Historically, Demo has been my favorite spec but its turned into an out right clunky mess to handle. But Diabolist Destruction has turned out to be like, the exact way I’ve been wishing it worked. Damage profile coming from yourself mostly, with big specific summons popping in for massive damage. Miss the fel guard, but I like not being forcefully tied to only one pet.
As for your proposed changes to destro, I wouldn’t be huge on them. Though I like the ‘Rifts are easier to take’ energy.
For destro specifically, only thing I really wanna see, for now, is baseline cataclysm. Or if you wanna get wacky with it, cataclysm replacing rain of fire as aoe shard spender (like as a talent choice node to be clear). Make it so when it goes off it consumes the remaining time on immolate dots to immediately do damage, then applies a fresh dot.
Outside of that, if something akin to Grimoire: Fel guard and/or Summon Vilefiend found its way into the destro tree…well I’d be quite happy with that.