25 sets for back workouts and 30+ sets for legs are not out of the ordinary for this body-type if they’re training correctly and honoring their physique type. The Endomorph needs variety, intensity, high number of sets, brief rest times, higher repetitions, moderate to high weigh and complex sets (super sets).
So the cons of the whole body routine are that the workouts are lengthy, tiring and physically demanding. Also, if you have any weaknesses, it is difficult to focus on individual muscle groups and full body workouts are often dominated by compound exercises. While they are more favourable for overall development, some weak parts could potentially be neglected.
A typical Ectomorphic workout should focus first on a powerlifting type of workout, doing just bench press, squat, dead lift, within the first few months. The average leg workout should initially include 4-6 sets of squats for legs, going for as much weight as possible with good form, each time.