The fatigue that you are used to is just residual lactic acid build up, it doesnt really relate to the depth of muscle stimulation involved in your workout.
I used to do giant supersets of 20 rep breathing squat and deep stretch dumbell pullover for 12 reps- both to failure.
8 supersets and i was seeing stars, and had to scoot down the stairs of the gym on my butt. i have to say that the burn, pump and general 'zap' that gave me was always more intense than regular 6-8 rep squat or leg press ever did, even when pushing some respectable weights, yet even with the different percieved recovery rates, I improved mass on both systems.
As long as you give your all no matter which rep range you work to, you will see results. Take the quicker recovery as a bonus, not a negative effect