I have an easy solution to knock out several problems;

1. Remove experience gained from "trash" in FATEs. This will get rid of the harassment of players from finishing FATEs like Dark Devices.

2. Make FATE targets unkillable if they are not within the range of the FATE itself. This fixes the de-syncing issue where higher levels sometimes can't contribute.

3. Prioritize bosses and monsters and players in your party/alliance over everyone else. This fixes the blinking issues.

4. Reward only 20% of the total experience of proper levels to lower levels. This discourages power-leveling using higher level areas.

5. Give healers contribution based on how much health they heal and give bonus for reviving within the FATE circle but don't give any for overheals (Heal 400 points of damage, 160 is overhealing. Get points for 240). This fixes the healing problem in FATEs.