That’s really weird. I have tested WordAI and Spin Rewriter with Copyscape and the results were always 80%+ uniquness, even 90%+. I don’t know how u spun the content to achieve such low results, but this is definitely way too bad. As for the block spinning, I have to be honest, this is the first time I’m hearing of it and I will have to check it out when I have a bit of time, but generally, yes, in the best case scenario, you would manually touch your Tier 1 content to make it 100% human readable and as unique as possible. For lower tiers, you can do pretty much anything, but again, the better quality of content, the better results you will have. That’s in my opinion and experience.
From personal experience Spin Rewriter is the best! like I still use it today. Its so easy to use (Just copy paste and the program do everything) Because of this tool I managed to schedule content and articles for 3 years, do you know how much time and money I’ve saved?!?! A LOT!!! Also i high recommend you pick their mothly plan if you are still in doubt