Just out of curiosity, who are the top tier teams (and in this context I think discussion must be limited to Europe)? All international teams appear vulnerable or "imperfect" to me. France are World Champions and NL holders but are without a win in 6. Spain, Belgium, England, Germany - none without flaws there. I think on their day Portugal are as good as any.
My recollection of the away game was that we rode our luck early: Jota(?) miss and a penalty miss from a harsh decision. But a couple of incisive runs forward by Doherty and Coleman raised the tempo for us and got us into the game and we then played a really accomplished away performance: concede territory but keep them at bay and hit on the counter. We could have had a pen ourselves (Connolly) and we had 2 or 3 dangerous breakaways. It was an almost textbook away performance against a team that I'd rate as considerably better than us. Baz made a good save from a free kick late on and then came the two goals from a world class header of a ball but before that Portugal were getting a bit desperate.
I totally get the criticism of Kenny's tenure - most of it is deserved - but I think the performance in Portugal has to be acknowledged as very good. It's churlish to try to qualify it as "they should have scored first" (isn't that how football works?) or any other stuff like that.
As recently as Scotland away - Parrott scores / Browne doesn't handle the ball stupidly - we could have been appreciating a very good performance. We lost concentration and the midfield battle at key times it's true, but their midfielders are objectively better than ours.