Considering they are adding a item level restriction system to dungeons, the concept of what is considered 'under-geared' will change. Since if the game allows those people in the dungeon, then SE believes they have every right to be there in order for it to be successful and the players have one less leg to stand on. Sure they'll be people who expect you to be in full ilevel 70 gear +relic to do AK/CM, but it's their fault for using Duty Finder with those unreasonable expectations and if they come in to be a jerk about it they'll be subject to the same kick system as the players they despise.

Suffice to say, the pros will outweigh the cons. As long as SE does the math and knows precisely what gear is required for each dungeon.