I just checked multikey support added in 2.6.6. It looks like either I am misunderstanding details of this new feature or there are some issues:

 1. ausearch output
 ==================
 Single key, in raw mode, ausearch outputs key as key="singlekey1" while 
 in interpreting mode it is key=singlekey1. Multiple keys, in raw mode
 it is key=6D756C74696B657933016D756C74696B657934 while in interpreting 
 mode it is key=multikey3 key=multikey4. It that expected?

 2. ausearch key filtering
 =========================
 Consider the following cases:
 
   a) # auditctl -w file1 -k singlekey1
      # auditctl -w file2 -k singlekey2
      # rm -f file1
      # rm -f file2
 
      This produces two events now, one keyed with singlekey1 and 
      another keyed with singlekey2. Ie. 

      # ausearch -m syscall -sc unlinkat -k singlekey1
      # ausearch -m syscall -sc unlinkat -k singlekey2

      produces two events with their associated records. 

      Issue A1
      --------
      # ausearch -m syscall -sc unlinkat -k singlekey

      This should produce nothing because there is no such key, but it
      does, it outputs events associated with either singlekey1 or 
      singlekey2.

      Issue A2
      --------
      # ausearch -m syscall -sc unlinkat -k singlekey1 -k singlekey2

      IMHO more key parameters in ausearch should mean either "AND" or 
      "OR" (and it should better be explicitly stated in man page). 
      Hence I would expected either two events or none. But it outputs 
      only events associated with singlekey1. 

   b) # auditctl -w file1 -k multikey1 -k multikey2
      # auditctl -w file2 -k multikey2 -k multikey3
      # auditctl -w file3 -k multikey3 -k multikey4

      # rm -f file1
      # rm -f file2
      # rm -f file2

      Again, three sets of events are produced, each of them with two
      keys. 

      Issue B1
      --------
      # ausearch -m syscall -sc unlinkat -k multikey1 -k multikey2

      Again, if multiple -k means AND, command should produce single
      events with multikey key=multikey1 key=multikey2. If -k means OR,
      command should produce two events. And it does. Therefore it 
      looks like it works as OR. But then...

      # ausearch -m syscall -sc unlinkat -k multikey3 -k multikey4

      Outputs only one event which indicates that multiple -k works like
      AND and not OR.  

      Issue B2
      --------
      # ausearch -m syscall -sc unlinkat -k multikey2 -k multikey3

      This should produce either one or three events - first with "key=multikey1 
      key=multikey2", second wit "key=multikey2 key=multikey3" and the
      last with "key=multikey3 key=multikey4". But it actually outputs two events
      -  second and third. 

      Issue B3
      --------
      # ausearch -m syscall -sc unlinkat -k multikey
 
      Similarly to (A2) I would expect no events but there are three of them.

Item 1, yes that is expected. You can check the original design with audit-2.3.3 which was the RHEL 7 GA package. This bug is about restoring the old behavior broken during the TTY escaping work.

Issue A1, keys match on partial names just like file names. You can pass --word to match the whole word.

Issue A2, we can only search on 1 key. The last key typed in wins.

Issue B is related to the above. You cannot specify multiple keys to ausearch just like you cannot specify multiple files. The last item is related to partial matching. Add -w to make it a whole word match. I checked the ausearch man page for the -w option and see that keys is missing. I pushed an update to github to clarify that.

audit-2.7.4-1.el7 was built to resolve this issue.

Updated version numbers. Another bz mandated a respin to a newer version that fixed the problem.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2017:2008