Muslera saved them from many losses before, he has been in the club for a long time and he has been helping them a lot, with him gone and a horrible goalkeeper, they ended up being even worse on that front.
Midfield is near empty, nobody to note on that place, and attacking is not horrible with kerem and mustafa when they play but when they do not, then nobody else can step up. Long story short roster is horrible, go get Pep to manage this team and he won't be able to do wonders with this team, he would be better than this, but not championship level at all.
I believe they could have been in top 10 easily without a problem. They should be thankful that they are not too far ahead of that top 10 place, if they have some winning streaks by the end of the season (which they will face a lot of great teams) then they could maybe get into top 10. Only 2 game difference between 9th and them, so they could still get there. In any case, Torrent didn't had a great start at all.
I think that the problem with this roster is there is not really good chemistry between the players and in the field which is affecting them a lot. With this roster as you said it is absolutely possible to be in the top 10 places but now it seems to be really hard for them. And 15th is just not good enough for them and they obviously have to do better. They need some wins very desperately. But it will be hard to do as they are going to play against some really good teams.