In set 1 there seem to be less healing on champs and origins. In this set there is Light and of half of Berserks ultimates have healing as part of them. Light may be fine since a lot of the healing that takes place doesn't do anything since champs are at full health when it triggers.
But Berserkers strongest champs (Mundo and Olaf) are hard countered by grevious, along with Renekton. As is Beserkers are in a hard spot and once people understand that Red Buff and Morello's heavily shuts down Berserk (Again already on the weak side) the class as a whole will easily be shut down by one item on a AOE ultimate.
Does Grevious need to last 10 seconds and cut off 80% healing, why not 50% healing and last for 3-4 secs or something like that.