The Crucible is for me by far the biggest time sink. Now that you changed the daily mission from '1 battle' to 'all 12 battles' and tied it to the yellow chest reward, it's even more important. There's no avoiding it anymore.
I've been doing my best to do a full clear every day. What started as a balanced combat team eventually shaped into a full magic aoe nuke team, as more and more overpowered and obnoxious units were added to the game for whales to buy and show off. I currently run Mazir, Alecia and Taurus for nuking, since their ult gauge refills to (near)max after each battle, without having to take any damage. I add Osiris for mdamage amplification, and keep a fully charged Flora on the bench in case healing is needed. Zem and Valan rotate in front depending on the encounter. On 'safe' fights I try to substitute other characters with useful ultimates, so that they can charge up and be ready for use if needed. This setup lets me blaze through groups of normal heroes, and can even take care of the more dangerous units like Ezio/PoP, the marvel characters, Vulko, Petros (with some scratches), Goram, etc.
Then there are the obnoxious parties. The Ezio plague is mostly gone, but there are still some around. At least 60% have a Nilya. Armored Valan is showing up more and more. Today I had to fight three parties with the same cookie-cutter build - armored Valan, Hurok, Adeline, Ursula. Pets that provide shield on hp threshold make things even more difficult. Here I list some of the problematic ones...
Valan (centaur) - Awakened and wearing Armor skin (free reward on at least 2 occassions) is able to tank an entire party for long periods. Provides cover, starting barrier and permanent armor boost for whole party. Reduces efficiency of preemptive nukes. Buys time for others to activate ultimates. Draws attacks.
Nilya (ice mage) - Initial attack is scattershot AoE with high damage. Hides in back row. Low hp. Frequent encounters demand a strong source of hp recovery or a oneshot nuke party.
Medium threats - require one ore more ults to kill, high probability of unit loss or high damage unless countered:
Ezio (assassin) - Long invincibility periods, short windows of vulnerability. Invincible while attacking. Physical attacks are evaded or countered with extended invincibility periods. Ultimate deals very high damage to lowest hp target, only tanks survive it (with big hp loss).
Orkon (bandage guy) - Fast ult charge. Unstoppable ult. Possesses random player unit for a while. Leads to unit dying or losing a lot of hp.
Vulko (assassin) - Invisible. Attacks back row. Very fast ult charge. Unstoppable ult. Invincible for entire ult duration. Ultimate deals very high aoe damage.
Petros (lava monster) - Extreme tankiness. Counter damage when hit. Heavy aoe damage. Will wipe party if not killed quickly.
High threats - require multiple ults to kill, guaranteed loss of units or lots of unavoidable damage:
Adeline (puppet) - Unstoppable ult. Attacks back row with high ST + splash damage. Very tanky. Short window of vulnerability before exploding and killing back row. Restores hp unless killed. Death causes explosion unless battle ends fast enough (unavoidable if Valan in party).
Mirah (vampire) - Long invincibility after taking damage. Repeatedly attacks back row while invincible. High hp/defense. Very tanky. Drains/refills hp. Vulnerability frames not visually obvious, easy to mis-time ultimates if another enemy unit present. Will eventually kill everyone except tanks.
Ursula (paper doll) - Long invincibility after taking damage. Invincibility during attacks. Attacks Mid row. Very tanky. Unstoppable ult. Ultimate deals very high aoe damage. Will quickly kill entire party.
To sum up the Crucible's flaws:
1. Takes too damn long. 12 battles by itself is too much, and having to restart some multiple times just makes it worse. Auto-battle and Fast-forward are not viable in this mode due to the risk of losing characters (especially true in the presence of obnoxious enemies).
2. The stakes are too high. Especially for newer accounts, this is the place to go to unlock hard to farm characters (saves 80 soulstones). Getting 30 soulstones every so often is nice too. Plus the huge gold payout is a must-have to keep up with game's high demands (forge levelling, hero skill levelling, goblin trader event, pets).
3. Node difficulty is unbalanced. Some are blown past in 3 seconds, some are 15 minute roadblocks, and these can appear on any node and even multiple times.
4. The enemy parties are ridiculous. Most teams I encounter would in no way be viable for doing a crucible run. Instead they're built solely to cause as much damage as possible, not meant to last for more than one fight. Lately there's been a shift towards unavoidable damage.
5. The player is given limited ways to succeed. Flora, the underpowered day-1 unit that still has no awakening is the only one able to quickly heal the team (in general, there are only a few healers in the game). There is no back-row tank unit to draw the aggro of all the back row asssassination characters. There are only a few units that have enough energy efficiency/recovery to spam their ultimate every battle. We only just got revive potions, and their amount is limited.