What Mesanna was talking about is an alternative system for awarding monster loot for event bosses. It is a modification to how the current Top Attacker system works. Currently, that system simply awards loot to the top X number of people who did damage to the boss mob. The change she mentioned is that the event bosses will begin to award loot not only to the top attackers, but also to those who focus on healing instead of dealing damage.
The actual way it works is fairly involved, and it awards credit for dealing damage to the creature, taking damage from the creature, and healing the damage it deals. The idea is to reward all who assist in the fight, and not just those with the highest damage output. It intelligently assigns credit in a way that should minimize exploitation.
I'm not going to discuss the system in full detail. It's set up so that you can't end up #1 in the list if you restrict yourself to one role, but if you do a good job in one role then you'll likely end up somewhere in the top of the list.
Now, the EMs are not going to change how they give out rewards. They will still give rewards based on participation via the objects that you double-click, and they will still give rewards as loot from monster kills.
The only difference here is that the loot from monster kills will also become available to the top healers as well as the top damagers. If you prefer to play the dedicated healer role, your efforts will now be rewarded.