Something like "Group (collects senders' domains of multiple emails)"

I am ahead for once :)

See [Bug 26543] there is a bugfix for this. For gathering domains, you need to
create a "custom Template" - with that you can create a filter that auto
populates 
the condition with 

From - contains - %from(domain)%

I am using the same JavaScript functions that I developed for SmartTemplate4 in
order to parse the header of emails to reply to, hence a similar syntax to:

http://smarttemplate4.mozdev.org/variables.html#from

I will post a screenshot on how to generate the custom template.

*** This bug has been marked as a duplicate of bug 26543 ***

Created an attachment (id=8488) [details]
How to create a (multi) domain template

This explains step by step. Make sure you have the bugfix from [Bug 26543] in
place so you can collect domains from multiple emails. Note: if more than one
email is selected, your own domains (from your configured emails) will be
removed automatically as a precaution against unwanted "self-archiving".