I know, I was also a little uncomfortable about the entropic and dystopic weapons. But think of two examples:
- Fighter with Magic Dystopic Sword: Say a 20th level fighter, with a +2 flaming, shocking, frost dystopic greatsword (a +10 weapon). If he hits, he does 32 damage, or 46 on a critical hit.
- Fighter with Magic non-Dystopic Sword: If instead he had a +5 flaming burst, shocking, icy burst greatsword (also a +10 weapon), he could take a -3 attack roll penalty for power attack, and still have the same attack bonus as above. If he hits, he does 5d6+8, for an average of 25.5 damage. On a critical hit, he deals 5d6+4d10+16, for an average of 54.5. Plus he can hurt the Tarrasque and other monsters, while the other guy has a harder time bypassing its damage reduction.
It's kind of a toss-up there, but overall I'd say the non-dystopic version is better.
Now, here comes the real munchkined version, which I agree might have been a mistake.
- Rogue with a Dystopic Weapon: A 20th level rogue with a +5 dystopic shortsword (a +10 weapon). If he hits normally, he'd deal 11 points of damage. But if he gets a sneak attack, he'd do 71 points of damage.
- Rogue with a non-Dystopic Weapon: This guy has a +5 flaming, frost, shock, holy shortsword (also a +10 weapon). If he hits normally, he'll deal 4d6+5 points of damage, for an average of 19 (26 if the target is evil). In a sneak attack, he'd deal 14d6+5 damage, for an average of 54 damage (61 if the target is evil).
A skilled rogue, who uses good tactics, would definitely benefit from an entropic weapon, especially if he can manage to get sneak attacks regularly from flanking his foes, though most foes at 20th level should probably have some sort of anti-sneak attack defenses, like fortified armor or blur. Or they'll be undead, and be immune to crits.
At the time I wrote it, I wasn't thinking of epic-level characters yet, and since I don't own the ELH, I can't say whether it's too powerful at epic levels, though it probably is. I can just imagine some 100th level rogue sneak attacking with one of these things, doing 311 points of damage with each hit. Eek!
If I were to redo it, I'd probably put a cap on it to say that it can only maximize 5 dice of damage for each attack.