This is definitely true, but if for some reason the group AoE burst is low, there may be some adds left alive with low HP when the Debilitating Slime fades and they will reapply the buff stacks, which can be dangerous.
We're using 2 tanks, 2 healers and 6 DPS on Maloriak; I'm also using a Piercing Howl/Shockwave stun kiting strategy for the adds. The DPS unload their AoE right after the Debilitating Slime hits (there's a few seconds between the boss yelling about the green phase start and actually splashing the raid with the slime and we actually wasted one or two attempts with people starting to DPS the adds too early, e.g. wasting Howling Blasts before the slime hit) and that's enough to kill the adds.
We also tend to have pretty messed-up raid compositions, for example the last time we did it with a fire mage, a balance druid, two frost DKs and two shadow priests