It is important to note that if DoT durations were increased, we'd have more time to shadowbolt, which would result in a DPS increase. This also has negative PVP implications, as they'd most likely have to nerf either the dots or the shadowbolts damagewise, a detriment to more than one PVP situation to be sure.
Yeah, it's not really something I would expect they could implement. But this is part of the mechanics they've gotten themselves into by making combat so fast. There really aren't many options for them to simplify this in the sense that they don't want people to use dot timers. You either make them last longer so you have plenty of time to get to the buttons, or you get rid of buttons to begin with (By combining dots).
One other option that came to mind is spell queues, I suppose. Being able to set spell priorities and allow players to queue each spell upwards of 5-10 times and let them autocast until the queue runs down. That would make it so people wouldn't need to watch a timer. They would need to remove cast times for dots entirely for this to work, though.
The main picture of any of these changes has to be that they want people to not use a dot timer.
Talking about removing haunts travel time, or making it instant, wont fix this fact.