Characters - 30
gear - pretty complete up to this tier
efficiency - 30s is pretty typical but it does vary.
Time played - I don't know, it's variable but I've been playing a lot I probably get about 5 hours a night. Sometimes I can hop in or an additional 30 minutes or hour just to get a few things done. The first week I played substantially more on some weekend days.
Progression quest: Just finished enraged.
Shield: first shield took 16 AoWs. I have the ability to spawn ~5 AoW and just missing velk heads for 7 more after that so it's probably fair to say ~2 shields in the course of doing enraged could be expected.
UCV5: I finished 75/80 before the shard changes and just finished my first one right after finishing enraged. Now they are quite fast and I'm already pretty deep into my second ucv5. Based on my kill numbers I would have completed roughly 3.5 UCv5 in the process of doing enraged had this drop rate been around the whole time.
Mantles: Finished roughly 2 mantles to rank 5. The only significant piece in this is Relics of Norrath. The essence combine item is very similar to flawless GSOA from VP where it requires a much more valuable component (essence of kael) to make something that drops relatively often from Rot. Perhaps there is a relic combine I don't know about but they come rather slowly.
Armor: I counted armor pieces as a function of enraged kills along the way. At last check I had 650 enraged total had 82 pieces of armor. So a drop every ~8 enraged implying a player should expect 125 armor pieces over the course of doing enraged (an 18 man group needs 126 pieces total). Of course, 1/4 of this will be leather and in general you will get duplicates and rots. When I finished enraged my warrior had ~30/60 armor rot hand-ins. I should say, at some point I stopped killing DR so I hadn't used Ymir to supplement armor drops. Ymirs mechanism is huge for progression in that it lets you direct what pieces you get. He is also extremely common from my experience so that helps a lot avoiding situations where you get very unlucky with one piece. I've still never seen a chain breastplate drop from Voltanis, for instance, yet I have 3 full sets of chain thanks to Ymir. This is a good mechanism.
UW13: I finished 2 UW13s which means I had roughly 240 essences drop in the span of doing enraged (36 for NS augs). I also have been saving AoWs which seems to be good for like 2-3 per clear so I probably farmed the equivalent of 250-260 essences if you count those unredeemed heads.
Roxy Aug: My MT is on sparkling which I guess is the 4th rank. I'm probably slightly unlucky here because I spent almost 90k coins total on this last upgrade. Although RNG will be high here, I suspect most will be at sparkling after enraged are done.
Cold delivery: I skipped as many wolves, bears and sirens as possible while grinding enraged so I'm nowhere on this quest (3 of 30). I'll probably put some effort into this now. Right now this quest is tangential to most of the rest of the zone, not sure if that's good or bad.
Favorite features - I have a lot of positive things to say about the zone in general. I like that you have to keep your brain engaged and think things through. You need to pay attention to what you are killing (for instance, to shape the drops you need), you need to pay attention to kill order (for instance if you have a boss and a named up to not waste a possible boss pop or if you have too many in camp to kill animals first to avoid possible chains). I like that using your brain is beneficial to your productivity and as a result I've very rarely, if ever, felt bored in Kael. I like that the bosses have mechanics that are well-telegraphed and clear (compare to like zeixshi for instance). I like that there is a real sense of progression as you move through the zone, you will get more capable you will get stronger. I like that the content presents a real challenge that pushes players to hone their play. I like that there are tons of small things to work on (AoW spawn, armor, spells, UV5, UW, mantle, coins/augs etc) while you are progressing through the overarching "Long grind" of enraged.
Areas for improvement - I don't have much here. I think this is a good step but I'd love to see this approach to boss design continued as we move forward. I'd like more mechanisms more often so you don't just zone out while a blob of HP drains away; Ragnar is a decent example of this, without his second enrage the fight is basically done at 80%.
I guess one thing is that Kael is homogenous, the entrance is basically identical to the deepest parts in terms of difficulty. I think it wouldn't be a bad idea to have difficulty gradients or particularly difficult parts, VP had this a little bit, but it was bypassed by binding in the zone beyond the challenges. I think that aspect was a good feature of the zone.