I think Arsenal's main problem last season was their weak bench team. And so if any player is injured then they cannot make a suitable replacement. And because of this, there was a gap in the team. Arsenal's performances lost consistency due to injuries to several players. Their performance is stable.
I don't buy the cheap excuse of lack of squad depth as the reason why Arsenal capitulated, injuries are part of football and it can happen to any player, even if Arsenal had a complete squad all season, City would still have won the league, they have the experience and they know what it takes to win the EPL, this group of Arsenal players barely have that experience and that's why the pressure got to them.
Having said that, what happened to Arsenal last season was a lesson i expect them to learn from, and if they keep on learning and improving, they'll win the league sooner or later. They are making brilliant signings which shows what the club's intentions are, if they stick with Arteta, they'll be Premier League champions soon.