Zardnaar
Legend
Mechanically and in a game design/balance perspective. And I'm not talking about 2E being a paragon of perfection either.
For the most part I'm considering magic and the traditional lvl 1-9 spells. 4E did identify some big problems and essentially rewrite the game and created new problems for itself. So it was still effected by and flawed from the 2E to 3.0 transition.
One big problem is saving throws and how they scale. In old D&D saves genuine got better to the point you could expect to reliably save 75-95% of the time. This made save or suck spells very risky to use. Which also made warrior types useful to have around.
5E toned this down a bit and you can save every round. But the gulf between a good and bad save can still be very severe. Consider you get hit with a wisdom save (dex is probably damage, con probably poison or cold or another damage type). Level 6 I'll go with an 18 in your primary stat.
Cleric or Druid +7 (18 wisdom, +3 proficiency)
Wizard +3 (proficiency+ability mod probably +0-+2
Non proficient+0 (ability modifier) or even -1
That's a difference of up to +8 between a good and bad saves. Bad saves do not scale but DC's scale both off proficiency bonus but also the casters prime attribute. At higher level that's a 12 point difference between a good and bad save but the DC has gone from around 13 to 19. Your bad save is gonna flunk the save 85-90% of the time so a save every round doesn't matter to much. 3E you can flunk 95% of the time potentially even on your good saves. It's not to hard to guess what saves to target if you can't intelligence and charisma saves are good to target unless they're an arcane spellcaster of some sort.
Conceptually 4E at least got this right.
Magic and spell resistance. An AD&D 2E mind flayer was 90% immune to a spell effecting it and even 3E had a weakened form if it. The 5E version is mostly a joke due to saves and you can get around it partially via save for half spells or just use spells with no save.
You might be fine with this conceptually but remember 5E has resistance and immunity to non magical weapons in it. Defenses to weapon attacks are actually stronger than defenses to magic when the real problem is actually the spellcasting. And everyone has spells. On class tier lists Fighters, Monks, Rogues are normally near the bottom hanging out with the artificer a class weak at damage and spells.
Once again 4E did at least solve this conceptually by removing both weapon and magical resistances. Not the best solution imho but they correctly identified the problem at least.
My preferred solution to this is the 3.5 minis game where they had SR/MR of 6 or 11 and you had to beat that on a d20 roll for your spell to effect the target. Nice quick simple but I would add a 16 to that number range. Our new Mind flayer with MR of 16 in effect has 75% MR in AD&D terms.
This also has the added advantage of future proofing any broken spells added to the game latter on and ensuring martials remain relevant lattervas buffing them becomes a better strategy than risking 75% spell failure (or 50%). 25% is an acceptable risk to me to nuke away (SR6).
The final thing is damage dealing spells and scaling damage. In 5E cantrips scale direct damage doesn't. Outside of a few spells eg fireball direct damage and upcasting sucks. An upcast hold person to a 4th level slot effects 3 targets a 200% increase. Upcast fireball in a 4th level slot is a 12% approximately boost.
Scaling direct damage has never been a problem since 2000 or perhaps even 1989 2E. Uncapped scaling in a low HP environment (pre 2E) is a problem.
Remember the Warmage in 3.5 and the game breaking and dominating combos it could do? Neither do I and 5E bloated hit point total nerf that even further. The 8d6 fireball in 5E is roughly equivalent to a 3d6 AD&D fireball (sometimes 2d6 or 4d6 depending on encounter).
Direct damage scaling spells are not the problem with D&D at least in modern era. Fireballs last days of glory was 2E which died 22 years ago. It's only good in 5E compared to even worse DD spells.
These are the big three things still an issue now due to the decisions made from transitioning to 3.0. There's other things as well from way spells were cast/interrupted through to how fast 5E characters level but these are the big ones with fairly simple solutions.
1. Defenses that scale better.
2. Redo SR/MR or ditch that and weapon resistances/immunity.
3. Fixing direct damage spells relative to save it suck type spells (overlaps with 1).
I suspect they will go with rewrites and nerfs and probably screw that up via missing things.
And as always ban Kender.
For the most part I'm considering magic and the traditional lvl 1-9 spells. 4E did identify some big problems and essentially rewrite the game and created new problems for itself. So it was still effected by and flawed from the 2E to 3.0 transition.
One big problem is saving throws and how they scale. In old D&D saves genuine got better to the point you could expect to reliably save 75-95% of the time. This made save or suck spells very risky to use. Which also made warrior types useful to have around.
5E toned this down a bit and you can save every round. But the gulf between a good and bad save can still be very severe. Consider you get hit with a wisdom save (dex is probably damage, con probably poison or cold or another damage type). Level 6 I'll go with an 18 in your primary stat.
Cleric or Druid +7 (18 wisdom, +3 proficiency)
Wizard +3 (proficiency+ability mod probably +0-+2
Non proficient+0 (ability modifier) or even -1
That's a difference of up to +8 between a good and bad saves. Bad saves do not scale but DC's scale both off proficiency bonus but also the casters prime attribute. At higher level that's a 12 point difference between a good and bad save but the DC has gone from around 13 to 19. Your bad save is gonna flunk the save 85-90% of the time so a save every round doesn't matter to much. 3E you can flunk 95% of the time potentially even on your good saves. It's not to hard to guess what saves to target if you can't intelligence and charisma saves are good to target unless they're an arcane spellcaster of some sort.
Conceptually 4E at least got this right.
Magic and spell resistance. An AD&D 2E mind flayer was 90% immune to a spell effecting it and even 3E had a weakened form if it. The 5E version is mostly a joke due to saves and you can get around it partially via save for half spells or just use spells with no save.
You might be fine with this conceptually but remember 5E has resistance and immunity to non magical weapons in it. Defenses to weapon attacks are actually stronger than defenses to magic when the real problem is actually the spellcasting. And everyone has spells. On class tier lists Fighters, Monks, Rogues are normally near the bottom hanging out with the artificer a class weak at damage and spells.
Once again 4E did at least solve this conceptually by removing both weapon and magical resistances. Not the best solution imho but they correctly identified the problem at least.
My preferred solution to this is the 3.5 minis game where they had SR/MR of 6 or 11 and you had to beat that on a d20 roll for your spell to effect the target. Nice quick simple but I would add a 16 to that number range. Our new Mind flayer with MR of 16 in effect has 75% MR in AD&D terms.
This also has the added advantage of future proofing any broken spells added to the game latter on and ensuring martials remain relevant lattervas buffing them becomes a better strategy than risking 75% spell failure (or 50%). 25% is an acceptable risk to me to nuke away (SR6).
The final thing is damage dealing spells and scaling damage. In 5E cantrips scale direct damage doesn't. Outside of a few spells eg fireball direct damage and upcasting sucks. An upcast hold person to a 4th level slot effects 3 targets a 200% increase. Upcast fireball in a 4th level slot is a 12% approximately boost.
Scaling direct damage has never been a problem since 2000 or perhaps even 1989 2E. Uncapped scaling in a low HP environment (pre 2E) is a problem.
Remember the Warmage in 3.5 and the game breaking and dominating combos it could do? Neither do I and 5E bloated hit point total nerf that even further. The 8d6 fireball in 5E is roughly equivalent to a 3d6 AD&D fireball (sometimes 2d6 or 4d6 depending on encounter).
Direct damage scaling spells are not the problem with D&D at least in modern era. Fireballs last days of glory was 2E which died 22 years ago. It's only good in 5E compared to even worse DD spells.
These are the big three things still an issue now due to the decisions made from transitioning to 3.0. There's other things as well from way spells were cast/interrupted through to how fast 5E characters level but these are the big ones with fairly simple solutions.
1. Defenses that scale better.
2. Redo SR/MR or ditch that and weapon resistances/immunity.
3. Fixing direct damage spells relative to save it suck type spells (overlaps with 1).
I suspect they will go with rewrites and nerfs and probably screw that up via missing things.
And as always ban Kender.