Not sure why this isn't in the actual match report thread, but then again if we're focusing on what went wrong on the second half, fair enough.
This has indeed happened before, I think it was West Brom or Everton, maybe even both..
As for specifically this game, it felt like as if Villa was still worried of conceding another goal so they were still sitting tight defensively, then I'm not quite sure what it was exactly, but our attack was none existent and whatever we did Villa wasn't having any troubles, and so they were slowly moving up, trying their luck as if they were the ones with a two goal lead, then came their goal and they knew our attack couldn't do anything under a full pressure mount. If this was planned, then we got tactically played.
What seems to be the issue isn't our completely none existent offence at such a phase, but for some reason we feel the pressure as if this is like a champions league final against a very strong team.. There seems to be no direction or proper thought process to look at what they're doing, stop the flow of their momentum, find a weakness when they stretch to put the pressure on us and exploit it (as offence).. This is what, in my opinion is the making of champions, to put a goal in and then hold them back by simply keeping them busy with having to defend strong counter attacks. The worrying thing is Man City did this to us - though we had glaring defence issues - they saw we could come back and score just as much, but they focused on making sure they can stop the flow, work a weakness, which was our left/centre and widen the gap, not just settle for parking the bus.
Man City game, unfortunately was a defensive issue, as I don't think that's under dispute, as they kept scoring keeping the lead every time we tried to come back. But the ManU game was a goal on the first half and when they all know that we need to score, we simply did nothing special (attack wise) in the second half, so this boils down to, in my opinion the offence failing to do their part in both scenarios.
If we're a goal or two up, to put it simple; we should be taking shots on goal at least once or twice when we regain possession, very simple. Villa game, we did 8 shots, 4 on target, that is clearly not enough considering how we were offensive for most of that game.. Our passing should be safe and giving it away 2 seconds later from regaining it, even such a basic such as this was not done and that's what worries me. How are we supposed to win anything when we feel the pressure when we're up 2 goals?
But... I could be wrong and this could all be because they really didn't see Villa as a threat so they only took what chances that came to them.