I can see where you're coming from, and I would perhaps agree if you were just planning on doing NG and maybe NG+. My problem with elemental weapons is that their damage is capped, no matter what you do stat wise, plus they can't be buffed. That is a huge point for me, considering how most bosses are weak to the various weapon buffs you can use, and if you're going through multiple playthroughs and continue to improve your Int/Faith and increasing the damage output of the weapon buff you use, it will very quickly start to overpower the elemental weapons, by quite some distance in the end.
Of course, if you just stuck with the base Str/Dex you need for your favourite weapon and then turned it elemental, you could put those points into Int AND Faith and turn yourself into a walking magical weapon. That's also fun!
Edit: Just ran some basic numbers quickly....
My current favourite weapon is the Great Scythe, and with full stamina (192 Stamina), I can get 7 swings out of it before I run out of stamina. At +15 and 40 Dex, it hits for 476 damage. A +5 Lightning Great Scythe will hit for 500 damage. With 7 swings each, a +15 Great Scythe can theoretically output 3332 damage (476*7), while a +5 Lightning can output 3500 damage. So even with 40 Dex, it still doesn't hit harder than the elemental version.
Here's where it gets interesting though. As I'm a Dex/Faith build, I have 40 Dex and the Sunlight Blade miracle. With 40 Dex and the Canvas Talisman, I have a magic adjustment of 190. Using the Sunlight Blade miracle, which is Lightning damage, I can add an extra 342 damage per swing to my weapon (Magic adjustment of 190 * Miracle Adjustment of 1.8). With a +15 Great Scythe and the Sunlight Blade miracle, I can output a total of 5762 damage with a full stamina combo (818*7). That's over 2000 extra damage in a full combo.
Of course, those numbers don't take any damage resistances into effect, but it does illustrate the limitations of elemental weapons when compared to high level buffed variants.