"since you will loose half of your health when you share it"
So? There are players who could survive in a level with half of their health only. Besides, even if they die in the level and had their alt in the party, the alt could revive and revive the dead player.
The game is now heavily based on the fact that you CAN NOT be carried by 'higher leveled' players anymore. You have to pick up your own Crowns, you have to pick up your own heat, you can't use higher leveled equipment until you're proper rank, etc etc.
Adding this back would just add more people bringing Knights and Squires into FSC or Tier 3 and just reviving them right before the Treasure Blocks or at the end of the Elevator before the level so they can heat their stuff for free.