Few new recruits in key areas are essential, getting the fernandinho alternative and eventual successor is probsbly the most important issue this summer, after that, an extra forward/striker is needed and then theres a few other improvements we can make depending on whats available.
Above all else though, we have to find a different way through in games where it's just not working. I don't necessarily mean we need a big man up front to play route one football but we need something different. Barca had Messi for that, Bayern didnt have anything and it was telling when it mattered, we need to develop something.
3 shots on target in 2 games against Liverpool tells the story, apart from the first 20 minute blitz last night they looked comfortable at the back throughout the two legs and this isn't a Mourinho bus we were up against it was a team who's biggest weakness is their inability to defend.
We need to find a balance between playing the football we do and actually creating meaningful chances which means actually shooting from time to time.
As a side note, I'd suggest more emphasis on set pieces roo. With the amount of the ball we have, we get more than probably any other team but rarely make use of them despite having some of the best dead ball specialists in the game. I like some of our inventive short corners but we really should be scoring more from them, they could provide a valuable amount of goals, especially in games where we can't break through.