The ONLY adavantage to doing this on ilum is that no one in the group loses xp if there is a higher level in the group.
NOT an exploit, people. Just game mechanics.
1. Everyone gets bolstered. Also your bolster is calculated on the gear/ character level you came in on. A level 40 will bolstered to 14k HP even while wearing lvl 15 greens. Try leaving illum and then coming back, you'll be down to 10k HP.
2. Mobs spawn as fast as you can click a panel.