I've had Icewind Dale 2 for a long time, and I've played it a lot over the years. But recently it dawned on me that I've never actually beaten the game in a legit playthrough (in other playthroughs, I've either started the game at a higher level, started with powerful equipment, or simply didn't finish the game). Now that I have a much better understanding of 3e rules than I used to (I grew up with DnD video games but not with the pen and paper version), I decided to do a full playthrough of the game on normal mode, with no mods.
In Icewind Dale 2, there is a way to exploit the game's 3e experience system. Although being higher level causes you to get less experience, you can avoid this by staying at a low level and not leveling up. Being at lower level than you're supposed to will make the game much harder, of course, but you'll end up with more experience, and you'll reach a higher level once you decide to level up.
In my playthrough, I took this trick to the extreme. Right before reaching Guthma, the boss at the end of Chapter 1, I leveled up my party to level 6. I then proceeded to go through almost the entire game with a level 6 party (I chose to stop leveling at level 6 because at that level my warriors got an extra attack per round and my sorcerers got the ability to cast the amazing spell Fireball). I didn't level my party up until the middle of Chapter 6. By that point, they had enough experience to get to level 24, which is way over the level you're supposed to be by the end of the game.
I've always hated the 3e experience system, with how leveling up causes you to gain less experience, because I feel it takes away from the satisfaction of leveling up, which is one of the best parts of these games. It's especially bad in Icewind Dale 2, where you will often get no experience for beating an enemy at high level, even if the enemy is still dangerous.
However, in my recent playthrough, I discovered the real problem with the experience system in Icewind Dale 2. The problem is that many enemies late in the game just don't give enough experience.
Since I spent most of the playthrough at the same level, I got to see how much experience different enemies give at different points in the game. I could compare the experience given by enemies in Chapter 2 to the experience given by enemies in, say, Chapter 5. I was surprised by what I found. It turns out that enemies in later chapters often give less experience than enemies in earlier chapters for a party of the same level. For example, the wyverns in Chapter 3 give less experience than the wyverns in Chapter 2. Most embarassingly, the yuan-ti abominations in Chapter 5 only gave 450 experience each; in comparison, that's the same amount of experience I got for beating an Aurilite Frosttouch in Chapter 2. The Crystal Golems in Chapter 2 give 5400 experience each, which is a lot, and that's fine, but I didn't find any creature that gave more experience than that until the Iron Golems in Chapter 5. To give you an idea, in Chapter 3 you fight a White Dragon, and it only gave me 1350 experience. Which would be tougher to fight: a single Crystal Golem, or four White Dragons at once?
I think Icewind Dale 2 would be much more fun if enemies late in the game gave more experience, because then it would be much more satisfying to kill challenging enemies. I hate finishing a tough fight and getting no experience from it.