I wouldn't worry too much as they are dreadful. I don't think they've got anywhere near Arsenals box yet. Look like a Championship team.
That's the thing for me though, they are crap, they have been in the league the last couple of years too, it's just how much they want to win the Europa League.
Last year was the weakest team they've had of all 7 times they've won it, yet to win it they played PSV, Fenerbahce, Man United, Juve and Roma. At least three of those are Champions League regulars and the others aren't crap either. This season I think the Europa knockouts will actually be weaker so I wouldn't put it past them to go all the way themselves. Match them in how serious we take it though and we'd beat them.