Checkpoints are definitely needed. However; to keep people from just getting the boss cp and getting rewards there should also be a system requiring each player to pass each level up to the boss in order to gain the rewards.
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Pass. If you lose a teammate, what are the odds you'd be able to replace them with someone that has the CP? Besides, Bungie didn't seem to mind doing this in the raids, so why not here? A single PoE run takes much, much longer than any single raid CP.