Warped rotors will give you a lurching brake effect, as if the brakes grabbed and released rhythmically. (Which, essentially, they're doing as the warped rotor will give varying amounts of contact with the pad as it rotates) I don't know if the tires would really give you a pulsing effect through the pedal, more likely through the steering wheel.

If your idle is fine, then I would doubt it'd be the cause of your braking problems. You'd notice an uneven idle, especially at a stop. (At least, I did...)

anthony