Different than what I would do, but looks good.
Depending on the positions of the Gore Riders, you might only need a single Flagger for both units - which would free up a Flagger to bolster either the Ax or Morax. (Putting the Krudger with the Gore Riders also works.)
I have not yet faced the fury of a War Trombone, but with overlapping fields of fire, two would definitely make me hesitate to bring any flyers in range.
If you had the points, I might suggest a Godspeaker - in some ways the most effective spell caster outside of named characters and necromancers. (Only one Horde though, so not as big a bonus as the last time I faced a Godspeaker... who became Target #1 for that battle, let me tell you. (Given the Inspiring Talisman, and Julie placed her Godspeaker to be bolstered by two units, then used Bane Chant to bolster them in turn.)
The Auld Grump