Now that you mention it, I've heard that. Perhaps the guy I played with had bad earphones.
However I play RO2 on two PC's both pretty much the same specs GTX580 vs GTX570 16GB vs 8GB ram, SSD, Intel, etc.
On the new machine I'm using the Corsair HS1 USB headset with a built in soundcard.
http://www.hardwareheaven.com/reviews/1037/pg6/corsair-hs1-usb-gaming-headset-review-conclusion.html
On the "old" machine I'm using my old Audigy2 ZS with a pair of open paded Sennheiser PC 131
http://www.bestheadsetreview.com/sennheiser/sennheiser-pc-131/
I've had the Audigy card since the stonage and the mic port is not working as it should.
So I plugged the Mic into the mainboard instead, works fine.
Anyway. Not long ago I made the mistak of plugging the headset in the wrong 3.5mm Audigy port.
I had to remove the card to get the sound normal again.
Now when it was out i thought since I'm allready using the Mic on the mainboard why not use the onboard soundcard also.
I tried it in several games including RO2 but the sound was nowhere close to the dedicated soundcard.
The quality is like comparing MP3 to CD and I hated it, so I tried to install the Audigy card again and lucky it worked.
So I have played RO2 with 3 difrent soundcards. According to reviews the HS1 should be the best I have.
Well its not.. Audigy2 ZS and the "cheap" Sennheiser PC 131 is hands down the best.
HS1 comes in second just marginaly better than the PC 131 with onboard sound.
Oh and two days ago I got to hear the expencive Sennheiser headset i bought for my nephew.
http://www.hardwareheaven.com/reviews/968/pg5/sennheiser-pc-360-g4me-headset-review-conclusion.html
He's using onboard too and I swear that the cheap Sennheiser I use with the Audigy 2 ZS card is much better.
I'm not trying to win an argument, its only my honest perception on how it sounds in my ears.
So if you ask me.. Buy a dedicated soundcard and a pair of decent headphones and I higly recomend the Sennheiser PC 131.