As a fulltime freelancer I made a lot of mobile games with C2 for my customers and tested a lot of various features, and performance issues are not related to Pathfinding, LOS or any other CPU-related feature as various projects I worked with had a variety of features in and the issues was the same everywhere.
I can surely say that apps wrapped with Canvas+ have the best performance and in the big majority of cases it's the only one wrapper that makes the app work at steady 60 FPS.
WebView+ simply uses Crosswalk and is still better than WebView but in the huge majority of cases slower than Canvas+.
WebView, in theory, should perform well starting from Android 5.0 but unfortunately, that's just a theory and in the real case scenario, it just performs the worst of all three. I think I was able to use WebView only in 2-3 projects throughout the years I work with mobile apps. Those were not games, but simple apps without any dynamic content.
I tested apps on Samsung Galaxy S4, Samsung Galaxy S6, Samsung Galaxy S8, Ipad Air Pro, Xiaomi Redmi Note 2, Xiaomi Redmi Note 4, Sony Xperia Z (can't remember the number), and few others.
WebView and WebView+ perform very well only on devices like Samsung Galaxy S8, so one of the strongest available devices at the moment. This is a good news because it means that once such devices will become widely used, we will have no issues anymore. But for now, only Canvas+ performs on the level that the game is playable on majority of devices.
I don't know if it's a GPU fault, drivers or whatnot, but for the end user (and customers, so also developers) it does not matter. If I tell my customer that he can either have his game running at 45FPS with WebView or 60 FPS with Canvas+, then obviously he asks for Canvas+. Nobody cares what's causing the issue, people just pick what works better, and that's understandable.
So again, it looks that we will get rid of the performance issue with WebView at some point (few years I guess). But at the moment for a mobile game C2/3 developer, Canvas+ seems to be the only reasonable pick, unfortunately (unless he's making something very simple). I say unfortunately because working with Canvas+ is not comfortable. It requires you to learn what to do and what not to do. It's not fully compatible with DOM elements, Text objects, XML documents, TiledBackground and so on. Nevertheless if one wants to have the game running smoothly, he needs to learn all that.
Note that it's not C2 or C3 bug or issue because I used the same code for the test cases. It's purely about the WebView vs Crosswalk vs Canvas+.