Hmmm, first off, no to the point blank shotgun + barrier melee, that's a guaranteed kill. It has happened to me and it feels like shit. Even if the shotgun blast is off, if they're using barrier melee, they still win the fight via the overshield. Titans that see me coming have a very, very significant shot at killing me unless they panic, even without their super (which is an almost guaranteed win instead).
Second, unload with what?
It really isn't mega armor anyway, it's less than Titans get from their Barrier Melee which doesn't even require a super.
Shoulder charge? Should be a OHKO to anyone without an overshield.
Now, a shotgun to the face AND a melee? I could buy that.
They're not even CLOSE to easy to kill. I am sorry if I gave anyone that impression. It's just possible, it happens, and it is more practical than killing a Titan during Fist or inside a Ward, a Sunsinger as I built described way above, or a Void Bombing Warlock (people claim THIS is easy, but I've never done it personally).
It's a super. If you don't have yours, you are very likely to get murdered by it. But it's not unstoppable either.