The City Of Heroes and Villains development team have published an additional patch note to the February 12th live update of City Of Heroes and City Of Villains Issue 11, in reference to adjustments made to Taskforces, Strikeforces and Trials:

"Tasks

Spawns in Task Forces, Strike Forces and Trials will now spawn enemies for at least the minimum size required to start the Task Force, Strike Force or Trial.

For example, if a Task Force requires 4 players to start and a team of 8 start the Taskforce, the spawns will spawn for a team size of 8. If 4 players drop out of this Task Force leaving only 4 players left in the team, the spawns will adjust to a team size of 4. If 2 more players leave the Task Force leaving only 2 players, the spawns will remain at a team size of 4, since that is the minimum size required to start the Task Force."