I do not think Real Madrid will have easy time in Champions League with their current team. They have history of doing well in tournament but last year they got lucky because of mistakes made by other teams. They also won some games at very last minute. Other teams like Bayern Munich could have won if they made different decisions. This means Real Madrid did not just win because they were best but also because of things outside of their control. So I think they will face problems in Champions League with their current team.
I will even say that Bayern could have won if the referees had made different decisions, but that is no longer important. I agree with you that Real Madrid was very lucky in several matches of the Champions League. It is obvious that they have more problems now and this is already reflected in their results in La Liga, I think that in the Champions League they will be even more obvious because the opponents there are also stronger. But perhaps this will be more obvious at later stages of the tournament.
In football sometimes a team needs luck to win a match, I think that's a common thing. Even when it's something that becomes controversial in the end, but it still can't be separated from football. This will be part of football, I think. In fact, when Real Madrid won the Champions League title, they didn't get it easily. They worked hard to get that success. Apart from that, mentality also speaks volumes. You said they were able to score goals several times at the end of the match which ultimately made them win a match. Well, when that happens, their mentality will work, because when a team doesn't have a mentality, then when time is running out and they become desperate with everything. While Real Madrid is not a team like that, they will continue to fight until the match is really over, that's what is called mentality.