I'm still trying to break the habit of running in with my healer
I have the same issue, you're not alone.
I'm still watching how you control your druid though, very well micromanaged. When I lead with mine and start shifting, using displacer beast, etc. I can lose track of the melee pretty fast.
As long as you have a target selected, they are doing their job spamming DPS.
Targeting is a huge issue sometimes especially with the druid... you displacer beast in the other direction or kite around and your melee is no longer in your view so you can't select new targets... runaways or they do nothing.
For arenas where target obtaining is most important I've been using the arena bars on the side to select my targets. No more tracking them down!