Okay, then. Here are a few comments.
The previous version of Syphon Strike provided 1200MP per use outside of Grit, which is what we should really be comparing to, whereas the new version is 600MP. This seems like a huge loss until you factor in the native MP regain that DRK now gets which is 200MP every 3 seconds. If you factor that in, you actually get 1000-1200MP per combo rotation depending on where the 3s regain ticks land, so it is actually very close to what we were getting in SB as far as general consistent MP regain outside of buff cooldowns like Blood Weapon.
Quietus is arguably more powerful now than it was in SB, giving the 210 potency of the Dark Arts version of the ability but without any MP cost, so it is actually 50 potency more powerful than the standard SB version of Quietus. The only reason people seem to think it is now weaker is because of the previous dungeon tanking game-play of using the MP gained from Quietus to fuel DA+AD spam, which was removed because the devs felt that level of self-sustain was too powerful and so they removed it just like they removed the self-heals from Inner Beast and Steel Cyclone due to the self-sustain from spamming either of those under IR.
Quietus itself is now actually stronger, it's just the game-play around it that changed.
I have zero ping issues in regards to Delirium and I have seen virtually no complaints, until now, in regards to this. It is exactly the same in this regards to Inner Release and it works fine there.
Perhaps you are confusing Delirium with Blood Weapon, which according to another thread on the forums, may be having issues with not fitting in that 5th GCD attack potentially due to having a longer initial animation lock, potentially registering the bonus MP and Blood gained on hit instead of ability usage, or potentially a different cause. That and the fact that DRK's AoE abilities are spells and therefore aren't affected by skillspeed, resulting in longer recast times on them and then potentially not being able to fit 5 into Blood Weapon's buff window should be looked into.