One example of a balance solution could be to permanently buff health of a team when unbalance is detected by a difference in total levels between the teams.

Example:
Team 1:
  • p1 = 300
  • p2 = 50
  • p3 = 500
  • p4 = 600
  • p5 = 200

Team 1 avg level is 330

Team 2:

  • p1 = 100
  • p2 = 50
  • p3 = 450
  • p4 = 500
  • p5 = 50

Team 2 avg level is 230

On avg players on team 1 have 100more levels. So we need to buff the bad players on team 2 to help make up the difference. We give 1hp for each level of deviation to the players who are below the average. As the avg level difference is 100 all players below level 330 will get 100 extra hp.

So on team 2 player 1, 2 and 5 will start with 100 extra hp to help them out.