To elaborate on Anon's defensive tactics of "run up to enemy", it's consistent enough, but when it doesn't work your unit is as good as dead.
When you run up to enemy it will most of the time either try to shoot you(even if it holds also melee weapon), and most likely miss or move away and do nothing else.
There are few problems:
- evading shots in melee requires energy, if you run out of energy from running up to enemy you are dead
- if there are other enemies in los you are dead
- if you run up to enemy not from back you will eat potentially lethal amount of reaction fire/melee hits
- enemies can use explosives if you stand next to them
- it doesn't work on vehicles