Let's do a quick test. Imagine an item that covers half your inventory and adds:
5% Chance to Cast Level 23 Time Strike on Striking
5% Chance to Cast Level 5 Uldyssian Time Freeze when Struck
1% Chance to cast level 20 Death Spiral when Struck
+17 to All Skills
+8 to [Class] Skill Levels (+13 if Paladin)
Maximum Skill Level Increased by 10
Increase Maximum Life and Mana 50%
+1300 to Life and Mana
+9% Life/Mana Stolen per Hit
+175% to All Resistances
10% to Maximum Resistances
10% Fire / Cold / Lightning Absorb
Damage Reduced by 5%
Poison Length Reduced by 33%
+418 to All Attributes
+50% Bonus to All Attributes
65% Increased Overall Speed
65% to Spell Damage
+80 Energy Factor to Spell Damage
Adds 345 Fire Damage
Adds 345 Lightning Damage
Adds 345 Cold Damage
-30% to All Enemy Resistances (-20% Poison)
+X to Teleport / Jitans gate / Edyrem / Dark Summoning / Purify
50% Open Wounds
5% Deadly Strike
25% Chance of Crushing Blow
Enhanced Weapon Damage +120%
Total Character Defense Plus 45%
80% Better Chance of Getting Magic Items
525% Extra Gold from Monsters
5% Reanimate as: Groupie
3% Reanimate as: Normal-Elite of your choice
2% Reanimate as: Normal-Elite some choice
1% Reanimate as: Normal of your choice
Unlocks your Black Road Skill
Unlocks your Ennead Skill
300% Bonus to Attack Rating
+50 to Maximum Damage
Slows Target by 10%
10% Uninterruptable Attack
Adds Strength Damage Bonus: (25/256 per Strength)%
100% Chance to Cast Level 420 Blast Wave when you Die
50% Chance to cast level 49 Trinity Nova when you Die
75% Damage to Demons
+800 Crafting Points
60% to Experience Gained
Reduces all Vendor Prices 60%
10% Bonus to Summoned Minion Health
35% Bonus to Summoned Minion Damage
15% Bonus to Summoned Minion Resistances
Replenish Life +400
Cannot be Frozen
Half Freeze Duration (Kappa)
+16 to Light Radius (Kappa)
+600 Maximum Stamina (Kappa)
+1 Extra Totems
+ Ennead, LC2, Bremmtown, Sleep bonuses
+ Optionally Cycles
Impressive, isn't it? Well, of course no one is going to have all charms perfect or maybe even trophied at all. Regardless, that list is not too far from being accurate, as usually certain stats are capitalized (for example +Class Skills) so the difference is not that big.
no, this doesn't mean this item will exist. I'm just trying to illustrate the total amount of stats granted by charms
Why is this a problem?
Dependency - Necessity
Well as we know, the game IS in fact balanced towards having some of these stats above mentioned. By no means are you able to clear duncraig with no charms, it's almost a requirement to have some basic ones before you can succeed at this uberquest. Why is charms necessity bad? Many reasons, first it makes obtaining charms less enjoyable. If charms are required, they become regular quests and lose all their "uber" mystic. It is also bad because it prevents people from moving on. Some stats simply have such a big impact in the game (for example: 5% Max Resistances from Azmodan) that without them your character is so much weaker. This usually promotes the famous median stuck loop: need gear for charms, and need charms for gear. This leads to:
Median XL isn't all about: What build can beat all ubers?
Many builds have become non viable simply because they lack uberpower. Any build who uses some sort of complex mechanisms / skillswitch will usually get punished over the spam-one-skill build. So having charms being such a necessity, promotes mindless FotM builds. I know, I know, there will be always "the easiest op build to play" and people will pick it regardless of how balance paradigms change. The goal here is to simply make builds that are not that straight forward not get so punished when they first hit the end phase of the game.
Take another look at the stats displayed above. Some stats simply became un-appealing because you get them from your charms. For example, 30% pierce means you need 30% less pierce from your equipment. Basic stats like resistances, flat stats, speeds, which are crucial to a build now stick to you independently from you your gear. Those are just examples, but most stats become uninteresting due to charms. Who will pick an item because it adds +250 strength? Noone. People will pick procs over anything and just pump the hell out of all numbers instead. This kills gear variety big time.
Unwanted Skill Scaling
So... +25 to all skills definetly doesn't do much good to skill balance. This removes creative thinking when creating skill setups as skills which lack increasing returns or hard point bonuses are very likely to be ignored and become one point wonders instead, that become viable with such a huge boost to skill levels. This said, it's virtually impossible to have skills be balanced damage-wise once you take charms into account. Also, since these +all skills are divided into two types (+All and +Class Only) this has another unwanted effect which is increase the usability gap between class skills and oskills (mostly noticeable in skills like spells).
Unwanted Stat Values
Needless to say, such a high amount to stat points completely kills the point of strength and dexterity costs. If these values were lowered, not all wdm builds would be using Demonic Touch, would they? Some items have higher requirements to make access to that item difficult, and demand an investment in a specific stat to obtain it, or it expects the build using that item to be devoted to this certain stat.
I'm fairly certain that reducing the ridiculous amount of +all skills, damage cap would likely stop being a problem at all. Reducing numbers is something that needs to be done to soften the excess in the mod, after all, when playing median, it always feels like your screen is about to blow up. While this is in some part the essence of median, specific moments such as hitting sprite limit or getting disconnected from a game, should not be tolerated. In the end, it doesn't matter if median is about "D2 on steroids" if you cannot play it because your game froze.
What will happen?
All charms, rebalanced. Old charms = legacy = they're gone. I know that it will be a bit awkward for those who play Single Player. But if the goal is reached (lower charm dependency/effect in the game) it means it shouldn't be such a big problem for your character. Because to compensate, the game difficulty will be rebalanced accordingly. Not just because the change in charms, but much more things that will happen in 2016 patch. After all this is a balance/content patch - not only will new content be added, but old content will be modified so that more builds and items become viable. Performance will be better and the mod playability will become less grindy, less focused on learning documentation, less time in cube, in other words: more fresh, dynamic and smooth.