I don't have very strong opinions about other things but one thing I can talk about is CR4.
Chewy and I put a decent amount of time into the map to see how far we could push the times learning new things here and there. Significantly more time than anybody else.
During this update, VERY few people ever ran the map. For over a week there were 7 people on the Nightmare leaderboard in total. It is now up to around 20 compared to Coastal with significantly more, don't have the number off the top of my head but its in the hundreds.
The map is up there in terms of effort and difficulty put in. The only thing I could say that takes more effort than it is Temple of Polybius.
Temple of Polybius drops the best weapons in the game. Nothing compares to their stat rolls. CR4 weapons on the other hand are pretty much on par with Coastal in terms of ult chance and stat rolls.
Both maps require multiple people to get any decent time on it, rewards are account based etc. These maps have a lot of similarities, except for the rewards. The thing about this is that CR4 is on par with Poly in terms of difficulty and effort but takes longer and drops half the weapons. You also can't target a specific weapon you want without using an extremely suboptimal class in most cases. These things should be on par with Polybius' weapons stat wise just considering how the maps function relative to eachother.
Now, the real problem at hand. The Kraken. There isn't much to be said about this thing other than, it sucks. It doesn't deal even moderately close to enough damage to make it usable. Nearly 500 upgrades with a max damage roll is absolutely insane just to beat a chicken on melee damage that can be gotten in a few runs. They need extreme buffs to their melee damage to ever be considered usable.
Even more of a problem, their ult rates. They drop ult or higher less than 10% of the time. This map takes 10 minutes if you're doing it very well in a 2p run. Anything above 2p gets incredibly laggy to the point that I don't care if it was faster, its basically unplayable for the people who aren't hosting. It's already incredibly hard to even get a hawk off on a Barbarian on 2 player due to lag, regardless of connection. You get 1 Kraken per run. Needing to do 10-11 runs on average for an ultimate immediately means they will not be farmed at all, they could beat chickens at 350 ups and still nobody would use them because it is so ridiculously rare to get one for a map this difficult and engaged. To be quite honest, depending on the damage buff that they require, they should be brought to a 50% ult rate. It feels really bad on a map that only drops 1 of a reward you're looking for to have a low ult rate.
A personal opinion is that I would like to see them beat a 39k chicken at 350 ups assuming max damage roll with a 35-40% ult rate. Another number I think could be looked at is beating it at ~400 ups with a 50% ult rate. Anything below 30% and I honestly couldn't see many people running the map regardless of how good they are.
Krakens roll pretty well on their stats so no complaints about that but might be necessary to bump them up for the sake of their ult rates without problems elsewhere.
The Kraken's ranged attack is pretty uninteresting and mediocre but I've heard there is already work being done on that so I won't bother talking about it.
Genie Kings are basically the same pet without ranged damage and give mana instead. These things should be buffed too obviously since they basically have the same numbers as the Kraken but I do think they should deal a considerable amount less than Kraken but give more mana. They really don't have a usage currently. The mana isn't enough to mean much for a DPS pet, could do with a small buff to mana to give it a purpose even if it was outclassed on raw damage.
Edit: I've been complaining about the Emerald Staff for a long time now but apparently never added it to this post after getting so worked up over the Kraken (please fix this damn pet).
The Emerald Staff was buffed to more acceptable stats, this was a more than welcome buff but in the process had its drop rate destroyed by a base damage nerf to intentionally make them worse tower weapons. This honestly just makes no sense. There is no logical reason that a weapon from such a difficult and slow map should have such a low ult rate, especially when this even guts the original intended use of the weapon for DPS. The Emerald Staff is obviously a particularly nice weapon to make an alternative to Clavas due to the movespeed it gives.
In reality, everybody just wants an alternative to Clavas, most people are more than willing to take a stat hit when compared to Clavas for better drop rates, people that already have good Clavas will probably stick with theirs. Akatiti has had the best staff in the game for way too long for such an easy map, give it up.
TL;DR. CR4 is a complete flop rewards wise. Very nice map now that a wave was removed but lag issues really hurt it.