C. you are discovered, but have enough agility to dance close enough to ur target to get a strike.
other than that ya sneaking up is pretty much the only other time.
infiltrator phantoms will most likely still get less kills than an enforcer constantly raiding the enemy base with heavy weapons.
the only diff is that people really despise being killed on their own turf with a strike to the back. but it takes skill to not be seen and make kills on hostile ground, and if a combat role takes skill and is worth it (meaning ur first kill isnt the death of you), i'm all for it.