We've had a lot of great feedback in this thread, but one thing that we haven't seen a lot of feedback on is suggestions to get players back to the XP/minute and general questing speed that was taking place prior to Update 59. We have seen a very significant increase in general speed of play since our recent lag reduction work, and as players have noticed, it's causing issues regarding game performance. Some of the goal here is to get players back to the pace they were prior to those recent changes. So, just to ask: How would you reduce player speed as it were to pre-Update 59 levels?
Well lag reduction
per se will increase overall speed even though I doubt to the level you are describing!
However I think the main challenge here is finding a balance between Devs (slowing our time in quests) Vs. Players (not slowing down the tr process) and the only way I can come up with is immensely buffing optionals. Tying kills to xp is, bar some specific quests, not a good fix at all; we want alternative ways to interact with the content (stealth, skills, etc), not to tie progress exclusively to killing!
Optionals generally involve lengthening travel through the quests hence lengthening the time of completion but the xp/min crowd (actually we all are, just to varying degrees!) will never take to this unless xp and, as someone else mentioned, possibly loot incentives were tied to these objectives.
However, even this might not be a good fix since if I've understood, the problem isn't the 'time in quest' but the 'mobs active in quest not being killed' and for this, instead of asking the players to mop up, a change in mob behaviour is the only way to do it (eg : mobs have guard duty and mustn't leave an area to chase after players and hence go passive, instead of a pack of 10 replace with one red and 2 henchmen, etc.).
The other alternatives like reducing player power, striding bonuses, etc. I truly hope are not being considered! Rather, in future content have encounters with longer interactions (not hp bags but things like the steal idea - love it!) but appropriate xp rewards. Any attempt to delay our progress will be the hair that breaks n.x camels' backs, it is already excessive...