We are aware of performance problems when editing a page containing a View block and that's actually a key focus of the current development cycle (for Blocks 1.6), trying to make it much more responsive and dependent on far fewer server requests than is currently the case.
So you should expect to see significant improvements when that becomes available.
The only thing I can point to in the meantime are two settings which can adversely affect page load time on large sites.
The first is the View setting to not include the current page in results (this is on by default, but is often not required).
The second is the option to show only filter values that would produce results (screenshot), that can have a performance impact both on the front end and the back end.
If the only remaining issue is the page load speed, given the development work currently underway for Blocks 1.6 I think we can probably close here.
Ok, but I don't know and I don't have understood what is for the setting "not include the current page in results".
I have found another bug in the View Block. Into this content template, hidden link, I have a View Block where the result to be displayed is only in View Loop > Loop Template. Here the I have added a link. The original and temporary URL I have used is "hidden link", and I try to change it as definitive with "hidden link".
If I update the Content Template and I go out, the link works fine. But, if I reopen the Content Template and after I go out without changes, the URL returns to the original and temporary URL.
New threads created by Nigel and linked to this one are listed below:
About the page load speed, and the Blocks plugin or Views plugin, when in the sites I use them, and I use the custom search form, all pages, also the pages where there isn't the custom search form, I have 3sec to generate the HTML.
The new update of Blocks and Views speed up the HTML generation?
The page load time for pages with Views will rather depend on the size of your site and your server resources.
There are certain things that can slow down generating the output of a View.
One is the "Don't include the current page in the results" setting (although this is minor except on very large sites).
Another is when you have custom search filters, the option to "Show only filter options that would produce results".
Another is when the output section of a View contains many conditional blocks: these require computation, and if your View was outputting 50 posts and the output section contained 3 conditional blocks that would be 150 conditions that would need to be calculated, for example.
Paginating results can lower the page load time.
Some blocks will be more expensive than others to generate. A Single Field block displaying a simple post field is very cheap, whereas the same block being used to display the post excerpt may require the excerpt to be calculated on the fly for every post in the output, for example.
The changes currently being worked on in the new development cycle mainly relate to improving the performance of the back-end editor for Views and templates.