If you are using a lot of visitor groups you could consider the visitor group usage gadget which helps editors see the visitor groups that are being used on page and on other referenced content. I maintain that gadget so confirm it should work on all versions of Episerver from v8 upwards:
In the scenario where you want more than one block to be personalised by one visitor group then you could consider using a container block. Example here: https://github.com/episerver/foundation-mvc-cms/tree/develop/src/Foundation/Features/Blocks/ContainerBlock. This would allow you to group one or more block(s) into it then you can personalise that which may reduce the total number of personalised groups on a page.
If you wanted something more descriptive you could also/instead use the container block instead of a personalised group and add the personalisation rules in the container block but this does hide some of the personalisation being applied.
Given both scenarios above creates some nesting then I would also recommend you take the Episerver Block enhancements package which allows inline editing of blocks:
Would you like the group title to be automatically populated (i.e. concatenated list of items used in the group) or rather added manually? This is something pretty easy to implement.
About putting multiple items in a single rule - it sounds reasonable as a feature request. It is not possible to achieve that in any way as of now and I imagine will be hard but it shounds like a nice enhancements for the editors.
We have a solution in which our customer makes heavy use of personalized groups and visitor groups. This works fine in some areas, but as the number of groups rise, it gets much harder for the editor to maintain control.
Do you have any tips to avoid content areas like this:
A simple title for each group could do a lot, alternatively it would be optimal if a single group actually could contain more than one block per rule. Right now we have a lot of groups with the same rules that just inserts a single block: