And from the other side of the coin, in minigames, a pre-heal is a good thing. You don't need to wait until someone is taking damage to hit them with a blue heal. Even if someone is at full health, throwing a blue on them is beneficial as they head into combaot. Before engaging the other team, try to group up in front of your healers so you can all get the blue running on you at the same time. This is not just for healers, but for all players.
It's a good idea for a healer in minis to remind players in group chat to group up for blues right before engaging the enemy. In the chaos of battle, you can't always run around hitting everyone with the blues, so having them running from the start is a big help.