Here's my initial review:
debian/rules should have get-orig-source target that handles the upstream ISO/tarball processing (Policy 4.9, see https://www.debian.org/doc/debian-policy/ch-source.html#s-debianrules)
This should not be a native package (as listed in debian/source/format) as it comes from an upstream source and has patches on top of the upstream code
debian/copyright isn't in DEP-5 format (http://dep.debian.net/deps/dep5/)
I don't believe you need the empty postinst and prerm scripts
Should be arch:all since there isn't anything that's architecture dependent in this package.

Source lintian output:
N: Processing source package xe-guest-utilities (version 6.2.0-1120-0ubuntu3, arch source) ...
W: xe-guest-utilities source: native-package-with-dash-version
N: 
N:    Native packaging should only be used if a piece of software was written
N:    specifically to be turned into a Debian package. In this case, the
N:    version number should not contain a Debian revision part.
N:    
N:    Native source packages are sometimes created by accident. In most cases
N:    the reason is the location of the original source tarball. For version
N:    1.0 source packages, dpkg-source determines whether they're non-native
N:    by looking for a file named <package>_<upversion>.orig.tar.gz in the
N:    parent directory, where <upversion> is the upstream version from the
N:    most recent debian/changelog entry. For version 3.0 packages, check
N:    debian/source/format for an erroneous "(native)" package format.
N:    
N:    Severity: normal, Certainty: certain
N:    
N:    Check: cruft, Type: source
N: 
W: xe-guest-utilities source: quilt-series-but-no-build-dep
N: 
N:    The package contains a debian/patches/series file usually used by quilt
N:    to apply patches at build time, but quilt is not listed in the build
N:    dependencies.
N:    
N:    You should either remove the series file if it's effectively not useful
N:    or add quilt to the build-dependencies if quilt is used during the build
N:    process.
N:    
N:    If you don't need quilt during build but only during maintenance work,
N:    then you can override this warning.
N:    
N:    Severity: normal, Certainty: possible
N:    
N:    Check: patch-systems, Type: source
N: 

Binary lintian output:
N: Processing binary package xe-guest-utilities (version 6.2.0-1120-0ubuntu3, arch amd64) ...
W: xe-guest-utilities: copyright-without-copyright-notice
N: 
N:    The copyright file for this package does not appear to contain a
N:    copyright notice. You should copy the copyright notice from the upstream
N:    source (or add one of your own for a native package). A copyright notice
N:    must consist of Copyright, Copr., or the Unicode symbol of C in a circle
N:    followed by the years and the copyright holder. A copyright notice is
N:    not required for a work to be copyrighted, but Debian requires the
N:    copyright file include the authors and years of copyright, and including
N:    a valid copyright notice is the best way to do that. Examples:
N:    
N:      Copyright YYYY Firstname Lastname <email address hidden>
N:      Copr. YYYY-YYYY Firstname Lastname <email address hidden>
N:      © YYYY,YYYY Firstname Lastname <email address hidden>
N:    
N:    If the package is in the public domain rather than copyrighted, be sure
N:    to mention "public domain" in the copyright file. Please be aware that
N:    this is very rare and not the same as a DFSG-free license. True public
N:    domain software is generally limited to such special cases as a work
N:    product of a United States government agency.
N:    
N:    Refer to https://ftp-master.debian.org/REJECT-FAQ.html for details.
N:    
N:    Severity: normal, Certainty: certain
N:    
N:    Check: copyright-file, Type: binary
N: 
P: xe-guest-utilities: no-homepage-field
N: 
N:    This non-native package lacks a Homepage field. If the package has an
N:    upstream home page that contains useful information or resources for the
N:    end user, consider adding a Homepage control field to debian/control.
N:    
N:    Refer to Debian Policy Manual section 5.6.23 (Homepage) for details.
N:    
N:    Severity: pedantic, Certainty: possible
N:    
N:    Check: fields, Type: binary, udeb, source
N: 
W: xe-guest-utilities: extra-license-file usr/share/doc/xe-guest-utilities/COPYING.gz
N: 
N:    All license information should be collected in the debian/copyright
N:    file. This usually makes it unnecessary for the package to install this
N:    information in other places as well.
N:    
N:    Refer to Debian Policy Manual section 12.5 (Copyright information) for
N:    details.
N:    
N:    Severity: normal, Certainty: possible
N:    
N:    Check: files, Type: binary, udeb
N: 
E: xe-guest-utilities: postrm-does-not-call-updaterc.d-for-init.d-script etc/init.d/xe-guest-utilities
N: 
N:    An /etc/init.d script which has been registered in the postinst script
N:    is not de-registered in the postrm script.
N:    
N:    Refer to Debian Policy Manual section 9.3.3.1 (Managing the links) for
N:    details.
N:    
N:    Severity: important, Certainty: certain
N:    
N:    Check: init.d, Type: binary
N: 
W: xe-guest-utilities: init.d-script-not-marked-as-conffile etc/init.d/xe-guest-utilities
N: 
N:    /etc/init.d scripts should be marked as conffiles.
N:    
N:    This is usually an error, but the Policy allows for managing these files
N:    manually in maintainer scripts and Lintian cannot reliably detect that.
N:    
N:    Refer to Debian Policy Manual section 9.3.2 (Writing the scripts) for
N:    details.
N:    
N:    Severity: important, Certainty: wild-guess
N:    
N:    Check: init.d, Type: binary
N: 
E: xe-guest-utilities: init.d-script-not-included-in-package etc/init.d/xe-guest-utilities
N: 
N:    The /etc/init.d script is registered in the postinst script, but is not
N:    included in the package.
N:    
N:    Severity: important, Certainty: certain
N:    
N:    Check: init.d, Type: binary
N: 
W: xe-guest-utilities: binary-without-manpage usr/sbin/xe-daemon
N: 
N:    Each binary in /usr/bin, /usr/sbin, /bin, /sbin or /usr/games should
N:    have a manual page
N:    
N:    Note that though the man program has the capability to check for several
N:    program names in the NAMES section, each of these programs should have
N:    its own manual page (a symbolic link to the appropriate manual page is
N:    sufficient) because other manual page viewers such as xman or tkman
N:    don't support this.
N:    
N:    If the name of the man page differs from the binary by case, man may be
N:    able to find it anyway; however, it is still best practice to make the
N:    case of the man page match the case of the binary.
N:    
N:    If the man pages are provided by another package on which this package
N:    depends, lintian may not be able to determine that man pages are
N:    available. In this case, after confirming that all binaries do have man
N:    pages after this package and its dependencies are installed, please add
N:    a lintian override.
N:    
N:    Refer to Debian Policy Manual section 12.1 (Manual pages) for details.
N:    
N:    Severity: normal, Certainty: possible
N:    
N:    Check: manpages, Type: binary
N: 
W: xe-guest-utilities: binary-without-manpage usr/sbin/xe-linux-distribution
W: xe-guest-utilities: binary-without-manpage usr/sbin/xe-update-guest-attrs
W: xe-guest-utilities: binary-without-manpage usr/sbin/xen-vcpu-hotplug.rules
W: xe-guest-utilities: executable-not-elf-or-script usr/sbin/xen-vcpu-hotplug.rules
N: 
N:    This executable file is not an ELF format binary, and does not start
N:    with the #! sequence that marks interpreted scripts. It might be a sh
N:    script that fails to name /bin/sh as its shell, or it may be incorrectly
N:    marked as executable. Sometimes upstream files developed on Windows are
N:    marked unnecessarily as executable on other systems.
N:    
N:    If you are using debhelper to build your package, running dh_fixperms
N:    will often correct this problem for you.
N:    
N:    Refer to Debian Policy Manual section 10.4 (Scripts) for details.
N:    
N:    Severity: normal, Certainty: certain
N:    
N:    Check: scripts, Type: binary
N: 
W: xe-guest-utilities: maintainer-script-ignores-errors prerm
N: 
N:    The maintainer script doesn't seem to set the -e flag which ensures that
N:    the script's execution is aborted when any executed command fails.
N:    
N:    Refer to Debian Policy Manual section 10.4 (Scripts) for details.
N:    
N:    Severity: normal, Certainty: certain
N:    
N:    Check: scripts, Type: binary
N: 
W: xe-guest-utilities: maintainer-script-ignores-errors postinst