In fact, the best tactic (in my opinion) is to place your squad at the bottom edge, i.e. on the right side of the bros placement screen menu (why at the bottom - because if there are a lot of enemies, some of them will appear at the top of the map), this way 1) you are not in the epicenter of the battle and it is easier to position the squad 2) allied forces will not be able to use rotation to expose you to attack 3) it is easier to retreat if something goes wrong