As long as you put some investment in a offense statistic, you'll find the game is moderate in difficulty. For a warrior this is strength and for a rogue this is dexterity. Constitution is not as big as you get spells that add 4 points to it and you do not always get the most when you level. When you get familiar with the way it works you can make some interesting combos that might not seem like the best idea,
Barbarian for one. You can give him a decent strength to start 16 or so. Give him 16 to dex and 12 or 14 constitution. Only put points into dexterity and wear a medium armor or light armor and he will be strong enough with rage and the dexterity will make him get hit less. The warrior classes can get away with that. God I love 3rd edition! Tyrants of the Moonsea for Neverwinter Nights1. It was originally supposed to be a main mod. It has a certain evil character from forgotten realms in the mod. That is all I am saying :)

Counter-intuitively, rogues actually work better with strength than dexterity. Single-classed rogues don't have enough feats or base attack to make two-weapon fighting effective, so there's actually not a lot a rogue can do with high dexterity. It's one of the design oversights with the class in 3rd edition, thematically painting rogues as a high-dex class but in practice making strength a better option for them.

There's no reason to go above 14 dexterity with a barbarian. This already leaves you max'ed out when wearing chainmail, so the AC gains are diminishing beyond that point. Pump strength instead.

Ye gods, yes, I love STR-based Rogues. Even though many of their skills are DEX-based, you can easily build a very effective 'skill' Rogue with high STR and moderate DEX. And when you run into monsters that are immune to sneak attacks, you've got another way to deal damage and aren't hosed like DEX-based Rogues can be in that situation.

Throw in some FTR levels and you've got one hell of an effective adventurer, IMO.