Greetings!
Thank you all for your feedback, it's much appreciated! 
About Warlock/Scout
Greatest problem of this class is global cooldown of Sace's Impatience skill (ID:1490582)
We use Severed Consciousness so often in this class. It takes almost 2.3 second to finish all psi. And we use this global cooldown skill to refresh our psi. This is really slowing down warlock/scout. My suggestion is to remove global cooldown from Sace's Impatience. I am sure Warlock/Scout will perform better. And this is what this class needs right now.
You got a point there, I noticed the clunky GCD myself as well, it will be fixed within the next magical balance patch. There are some other class changes planned before, so it might delay by a little (perhaps next week or so).
2. Psychic Shot (ID: 1490579) isn't part of any optimal rotation currently. It's damage is way too low to use compared to Severed, and it has no utility that would make it part of the rotation either. If it at least recovered 1 psi per hit, you could use it to recover Psi in-between Willpower Blade but otherwise I don't have many ideas to make the skill useful. Maybe consider reworking the skill or removing it entirely in favor of some other mechanic or Matt buff instead.
We do not plan to change Psychic Shot for now. I could imagine pushing the single target potential while reducing the AoE potential even further (that might already be achieved by removing the GCD from Sace's Impatience), but the idea was to have Warlock/Scout in a special place aside of most other warlocks, so there are no plans to increase its area damage potential. My data shows it has decent potential at bossing already, such as Zhargos worldboss and similar. If you are looking for other single target classes that might fit your requirements, I would suggest checking out Druid/Rogue, Bard/Warlock or Priest/Scout. Those got some decent single target buffs within the last few patches.
Warlock/Rogue
1. The class was definitely overperforming in the past, and still does pretty well even after the 10% dark dmg nerf. It's the only Warlock class I can play with 180-200 ping (West coast, USA) and do similar damage to a Warlock/Mage. But it requires 2 weapons tiered and corrupted to get to the same damage values. I think it's worth considering adding back ~5% dark dmg to the Shadow Slice (ID: 621406) buff from Shadow Step.
2. The AOE damage reduction that was added to Ready and Waiting (ID: 621404) was a really nice idea, but unfortunately most AOE skills still hit for 1.4-1.8m even with the changes. Generally speaking, I haven't noticed any differences in the amount of times I die with the change. I do really notice the missing movement speed it was swapped out for -- the class feels a lot slower (and less fun) without the movement speed. I'd like it if the movement speed could be added back in place of the AOE damage, personally.
Good arguments, in my opinion the class is already very agile due to casts that work on moving, so a lot of movement speed isn't necessary, but bringing back the original 15% shouldn't hurt too much. 
The damage reduction was an experiment that wasn't working as much as intended, so we will think about changing it into damage reduction at full HP, maybe something around 40% should be more useful to prevent oneshots.
About the bonus damage, I need to wait for more consistent data to classify the class properly, so I can't promise any buffs into this direction yet.
Warlock/Mage
1. By far, this seems like the best performing Warlock class (IF you have low ping). Many other mdps classes seem fairly well balanced against eachother (various mages vs warlocks), but Wl/M really destroys the other mages when it has a good lua engine and low ping. The main issue is that we're doing 0.5s cast on Soul Brand Sting, but high ping can add up to 200ms delay between that Soul Brand Sting and when the cooldown for Flaming Heart Strike is reset. 200ms is ~40% of the cast time of the next Soul Brand Sting, so overall it can lose up to 40% of its dmg depending on ping.
2. The ping issue could be mitigated if Soul Brand Sting (ID: 498710) instead reduced the cooldown of Flaming Heart Strike (ID: 498697) by something like 5s, so you had to cast it 4 times before Flaming Heart Strike was able to be cast again. Then that ping delay would only occur every ~4 casts, meaning at most a 10% dps loss vs perfect ping. Of course there would need to be some damage adjustments to both skills to keep Wl/M around the same overall damage as before, but at least the ping issue could be mitigated.
We do not plan to change the cooldown system on this class for now, as it's a unique core mechanic of this class. The idea is to bring Warlock/Champion in line with Warlock/Mage in terms of damage soon, so it might become a viable alternative.
To clarify: Your issue is that you cast Soul Brand Sting 2-3 times additionally, because the Flaming Heart Strike resets with some delay due to lag? I'm not sure if a simple cooldown reduction of ~5s would solve this issue properly, as the CDR will be delayed as well. But I will keep this in mind for future changes. Feedback like yours is much appreciated as it gives insights into other perspectives.
Best regards
Wesker 
Even if there is no direct answer to your requests, it's all heard, considered and internally discussed.
