I have a LifeProof case on my iPad Air 2 and it has no ill affect on wifi.I have used it with the wifi from my modem for internet and with the app for GoPro and it works fine.Good distance with the GoPro app and no problem moving around the house putting several walls between the ipad and the modem.
But the LifeProof case is only plastic so there is nothing in it that can block or reduce wifi signals.
Has this problem only occured since using the LifeProof case and never before?