First of all we talk about html5. En that is still not the most performant and brilliant engine on the world. But, it works in all browsers. If you choose for Construct you choose for html5. I suppose that did not yet dawn to you.
Constuct is no more then a UI to write html5 code. Scirra did not make html5. But they do their best to adress all the inperfections of html5. One of those is performance. This is why you find choices all over Construct. A choice to do it 'that way' to keep it performant.
Only one obstacle map is one of those choices. So if you have 100 solids (if you choose for solids) running arround, rebuilding the obstacle map for one rebuilds the obstacle map for all. Hence, if the one thats supposed to find a path is an obstacle too, it will not find a path. If you had read the manual, you would have known this.
Next. The pathfinding behavior finds paths. Thats all. It avoids obstacles based on the gridsize and the cellsize you gave it. It does not know how big your sprite is. It is just what it is meant to be, an easy help for finding paths.
Not happy with it? No problem. Build your own pathfinding. You can find exellent examples on this forum. Yet none of them will account for the size of the pathfinding sprites.
If you think that pathfinding combined with physcis and ray tracing should be a basic option in a html5 engine, then let me ask you: why is that plugin not made yet ? There are plugins for almost everything.
I gave 1 example. And it is a complete AI. The logic that answers your question is in there in 1 event. I cant show the funtion of a steer when i cant build wheels under it.
I am sorry it did not meet your lazy expectation.
But i did not earn that sneer. No one did.