iPad issues ARE NOT related to the iPhone slowdown due to battery degradation/iOS 11 CPU slowdown code issues.
Batteries in iPhones are MUCH smaller and have a lesser charge/discharge life than one's in an iPad.
Your iPad Air 2 issues are totally unrelated to the recent older iPhone slowdown announcement!
And to date, YOU are STILL one of the very tiny minority of iPad Air 1/2 users still complaining of iOS 11 slowdown issues.
Why don't you simply backup your iPad, wipe it, set it up as a new device and try running it with just the base installed apps for a day or two to see if your iPad Air 2 returns to normal performance.
If it does, THAT means one or more of your installed apps is corrupt or the data within apps is corrupt causing all of your iPad Air 2 issues.
The ONLY way to remove ANY data corruption from an iDevices is to reinstall All of your 3rd party apps, one by one, then test that your iPad Air 2 is still running fine, then reinstall the next app and so on and so forth.
The iPad Air 2, the new iPad 2017 (iPad 5), the 9.7 inch iPad Pro AND the 4th gen iPad Mini all have 2 GBs of RAM installed and all of these share similarly aged (1 to 2 generations old) CPUs.
There have been little to no postings for many of these models running iOS 11.
So, clearly, something bad is going on with your iPad that has very little to do with iOS 11!