@MrZigaS
You just saved my life over here. We had to move to Appium 1.8.0 after the XCode 9.3 update and my scripts on iOS became glacier-like in speed. I was also running Java Client 5.0.4 but have now updated to 6.0.0-BETA5 (which required an update to selenium-java: 3.9.1). Before this update, one of my scripts running against an iPad Air took 66 minutes to complete. The same script after the update just took 5.5 minutes to run. It is still true that the Androids run faster in all cases but I am super happy that iOS devices take twice as long to complete instead of 20 times as long.
Thanks!