Remember that Engineers and Scouts are riflemen too. In a pinch, they can help gun down Xenos.
Specialisation
When you're upgrading troops and tactics, specialisation pays off. There's no point in putting generalists on the map. Make sure your Templars get better at doing what they do best.
Troopers
Troopers work best in groups, including at least one soldier who can be switched to overwatch to protect his buddies.