Unless you're the type of fan who loses sleep over your clubs transfer fees and salaries, it's surely better to have him than not. Even if he does continue his track record of injuries, I'd prefer him over Perisic.
That makes 0 sense. If he continues his current injury record he would not be fit for more than half our games. Not only should you prefer Perisic over that, you should even prefer signing no one over that.
Last thing we want is another Rooney situation where a high profile, high salary player is on the sidelines every week with the reporters asking the same questions about him over and over.