It chokes on my iPad Air too. Will probably replace it with.a Surface Pro 4 when they come out. Not really a fair comparison, because the surface is a more expensive option, but I like the idea of having a full computer. Then I will be able to run whatever ad blocker I want.
My suspicion is Apple won’t enable this ad blocker feature for older devices. We’ll have to wait and see.
If your device can run OS 9, it will run ad blockers.