Best Of

First, I just want to say that Chaos Trials are great addition to the game.  They are a lot fun, challenging, and rewarding and fill in the end-game gap in content (and rewards) that was missing previously, but I feel like the difficulty at higher tiers could use some work. 

Difficulty:

I will be honest here, the tier scaling feels like a quick-fix way to make the game mode harder.  It is like when an FPS game wants to make their game seem more difficult by simply increasing the health on everything to the point that every enemy is just a bullet sponge.  The game isn’t mechanically harder, but artificially harder, in the sense that the player still plays identically to how they normally would but end up losing simply because their character stats aren’t able to overcome the absurdly high HP the enemies now have.  That is exactly how the tier scaling feels after the recent hotfix.  Mechanically the game is the same difficulty as before but now players are leaking mobs out of their killbox simply because it is mathematically impossible for their capped hero/trap stats to counter the increased enemy HP in certain circumstances.  Personally, I think players should lose because they failed to adapt to the modifiers rather than just being overwhelmed by scaled-up enemies.  Currently this is not the case.  Most of the time the difficulty of Chaos Trials comes only from the map order and innate scaling rather than the mods. 

This is especially apparent for Mercs and Unstable Rifts that become unkillable at T11-T12 on early waves for most of the heroes.  It is literally impossible to kill the Rifts before they open on the majority of the larger maps on the higher tiers if you are not using Midnight or Blackpaw (quick, high-burst heroes).  The Mercs seem to walk through 6-8 BGH traps and only lose 50% of their HP (or commonly 0% of their hp in the case of the gnoll breeder or dwarf priest because of their mechanics: breeder gnolls steal shots; preist shield blocks shots).  Then you try to finish them off with your hero and it takes you literally 20-40 seconds of continuous damage just to take off the remaining 50%.  It does not really feel fun or challenging to deal with them, it is just tedious and frustrating.  Mercs are supposed to be mechanically difficult to deal with, but easy to defeat if you understand and exploit their weaknesses.  This balance is completely broken with the way they scale up.  For example, the Dwarf Priest is supposed to be an easy kill if you run into his shield to kill him but with the health scaling the priest ends up taking 30-40s to kill even when you are playing perfectly and exploiting his weakness.  Meanwhile he is buffing and healing every enemy near him and you leak half the wave because of this unkillable priest.  Is this actually hard?  Not really, it is simply artificial difficulty.  You are losing because of numbers, numbers you are mathematically incapable of overcoming because of the level and trap tier caps. 

Aside from the bullet-sponge artificial difficulty of the scaling, the scaling also disproportionately makes the early waves substantially harder than the later waves.  This is because the starting money is balanced around normal health minions, not minions with 6-8 times their normal health or extra heavy minions.  Take The Baths for example, this map gives you only ~7500 coin to start with, which is perfectly acceptable to deal with normal health minions, but when you’re on a T12 key with extra Armored Ogres and Shield Trolls, well, good luck.  It is literally impossible to complete that wave without leaking substantially because of how little money you start with.  However, once you make it past wave 2-3, and get enough money to actually build more than three traps, the map becomes trivial and there is no risk of leaking for the remaining 11 waves.  This pattern holds true for the majority of the maps.

Here are my suggestions to make the game mode feel more difficult without making players feel like they are losing because of over-tuned numbers:

• Reduce the amount of health scaling mercs receive substantially.  These enemies should be a mechanic/skill check, not a numbers/dps check.  If players counter these enemies correctly and intelligently, they should die quickly.  [Somewhat unrelated to Chaos Trials specifically: merc balance needs a lot of work.  The Gnoll Breeder and Dwarf Priest are so unbelievably overtuned even without Chaos scaling (partly because of their massive health pools and partly because they are practically immune to BGH traps) and the Assassin and iMage are completely irrelevant and have zero impact on the game – this is another topic all together, but suffice it to say that chaos scaling really highlights the merc balancing issues.]
• Unstable Rifts should not scale at all (or only with account level, not key tier).  These are again a mechanic/skill check that tests players map awareness and ability to build semi-self-sufficient killboxes and deal with leaks when they get back from killing the rift.  If players respond quickly to the Rifts they should always be able to kill them no matter what the wave or key tier is. 
• Make the enemy scaling based on wave number as well as key tier.  If done right, every single wave should feel as difficult as the previous for every wave on a given map.  For example, wave 1 might only receive 80% of the tier’s scaling and wave 14 might receive 120% (or higher if necessary to achieve the desired difficulty).  I believe the tech to do this already exists since this is essentially how it works in endless. 
• Map starting money should increase with key tier level, possibly around 250 extra money per tier, and/or extra enemy modifiers should grant extra starting money.  This will help make the early waves feel more manageable if players setup their traps correctly, instead of currently where it feels like you are starting a wave 30 endless map with only five traps.  At the very least certain additional enemy modifiers should come with extra starting money, such as the Armored Ogres, Fire Ogres, Shield Trolls, and Forest Giants.  This is to make it feel like players have a skill-based option to overcome these modifiers (more enemies -> more starting money -> use that extra money to place traps correctly to counter them = knowledge check) instead of losing/leaking simply because of their massive hp and no traps to deal with them.  Modifiers should always have a skill/knowledge-based counter, and additional enemy mods on wave 1 currently have no real counter because you don’t have the money to cleanly deal with them yet.  
• Increased trap cost modifiers are far too punishing on the first 3 waves compared to the rest of the game.  Consider making the cost increase based on number of placed traps in that category instead.  For example, the first trap in that category could be the normal price and then each additional trap built from that category could cost 33%-66% more until the mods price cap is reached (2x-3x).   
• Once these above points are addressed, if the mode is then too easy, consider buffing the modifiers to make the game mode mechanically more difficult.