I would love to have the animation of Incinerate changed, and more power added to Shadow Bolt. Currently the only spells in our entire arsenal I feel pack a punch (talking animation, not numbers) are Shadow Bolt (unglyphed) and Chaos Bolt. Incinerate feels like a homesick critter crawling its way to the target, that juts happens to be on fire. Malefic Grasp does feel powerful it its own way, but not the "TAKE THAT! HAH!" way of a pyroblast or shadow bolt. Now, it just feels like "yeah, yeah, yeah, I'm casting this and that and, oh, look at that - you're taking damage!".
I think they gave warlocks too many QoL improvements in this expansion to justify any further being added. I mean, what more can we possibly beg for? If you're a warlock engineer, you literally have no problems with mobility, no matter what you're doing. I can close a 300 yard distance in less than 5 seconds, no other class can even come close to that, and that's only because of our mobility. You might argue that such a thing isn't relevant because it isn't realistic in a PvE-environment (being the environment they design in I assume), but the list of funny and interesting QoL elements like that quickly add up.