These SOAP API's require usually either an emsGuid or hostGuid to operate as per the wsdl, if you want all returned, specifying * as an emsGuid or hostGuid would work.

Tested with SoapUI on 5.4 latest build.

New commit detected on manageiq/master:
https://github.com/ManageIQ/manageiq/commit/30bba7beb8c077e7cd0b1a8f36927c4cc789c47e

commit 30bba7beb8c077e7cd0b1a8f36927c4cc789c47e
Author:     Milan Falešník <mfalesni>
AuthorDate: Mon Apr 20 09:57:12 2015 +0200
Commit:     Milan Falešník <mfalesni>
CommitDate: Mon Apr 20 09:57:12 2015 +0200

    SOAP - count with default param not specified
    
    The underlying method getKlassList/getKlassListbyId counts with default parentGuid but the calling methods always pass something, even if it is nil. This should make the behaviour the same as in the EVM_vm_list which converts the nil to empty string and then matches it, so it will return * by default.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1212428

 vmdb/app/apis/vmdbws_ops.rb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

looks like already fixed by Milan. Reassigning/Setting state/.

Verified working in 5.4.0.0.26

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://rhn.redhat.com/errata/RHBA-2015-1100.html