As you might expect, I'm reading and watching a lot on E3 news. I might offer some impressions later. For now, I've got two words for you:
Dynamics are the name of the game, so why not make healing a bit more interesting? Imagine a grenade or vial of healing potion that you must smash against the ground. Throw it down at your feet and it heals you. Throw it by some allies and all in the area of effect are healed. But throw it too close to an enemy... and your enemy is healed.
This creates opportunities for many memorable moments. If your fellow player or AI companion is toe-to-toe with an enemy and hurting, you can try to aim your throw behind your ally so it heals him and not the enemy as well. If the fighters turn at just the wrong moment, you might heal the wrong person, or both of them, or neither. There might even be a possibility that the grenade can be batted while in the air... flying across the battlefield to land who knows where.
Even more, healing grenades might react differently to different objects. They might burn particular enemies. They might explode when they touch a particular metal, hurting friends or foes alike. If two healing grenades hit one spot simultaneously, the healing effect might be exponentially increased.
The basic idea is that, like the sticky grenade in Halo, there are countless possibilities that make each counter feel fresh and potentially surprising. Healing grenades might not fit a particular game, but all games should include at least one dynamic like this.