Not a big problem. Oversized two-weapon fighting is OK, but it's not a huge damage option. It's also expensive to enchant two weapons. With the way the game is currently constructed, off-hand weapons just don't add enough damage to be worthwhile without some sort of boost. That boost can come from a lot of places: extra dice like flaming/shocking/holy weapons, or sneak attack; special bonuses like the dervish gets or greater weapon specialization/weapon mastery; or power attack with oversized two weapon fighting or unarmed strikes. If you don't have one of those, you're giving up a shield bonus to AC or two-handed power attack bonus, at least 2 points of attack bonus, several feats, and lots of cash (for the off-hand weapon) to get something in the range of an extra 1d8+3 per round. That's just really not very effective. I think the designers realized after a time that it wasn't effective for anybody but rogues (who can boost two weapon damage with sneak dice and who can't use a shield anyway), and so you started to see a bunch of options to improve the efficiency of two weapon fighting. It is stylish and cinematic, after all.