Looking at healing done is the last thing you should do. It might just show that the people topping the rankings have been mindlessly following the bus. You should instead focus on anticipating objectives and moving to them fast and safely since most maps work like that. And if you're lucky to have competent people that also play the objectives you will have a lot of heal to do.

Also healers are tanks so make use of that and of line of sight as often as you can, be that for baiting of simply tanking while your group dispatches the enemy.

Practice, experimenting, learning how the maps operate and not looking at numbers will definitely make you a better frontlines player. Never underestimate the weight a single player can pull by playing smart.