I could be wrong by I don’t think Frost DKs have that many essential and required macros for PvE.
Mostly you need the “BOOM!” button, so Pillar of Frost + Raise Dead + [trinkets]/[other item perks].
Here’s a good guide
for Frost DKs with macros included from our good friends at Icy Veins.
and here's the macro that they recommend:
#showtooltip Pillar of Frost
/cast Pillar of Frost
/cast Raise Dead
Also I just checked on my DK and HoW does seem to trigger the GCD so unfortunately I’m afraid you can’t do that with a macro as that would only work with a /castsequence and since HoW has a cooldown it would only work every 20 seconds, besides you would lose time because of the GCD, so that wouldn’t be a good idea anyway DPS wise.
Use HoW only if you have some downtime to spare, otherwise using it (if you’re still buffed) is probably a dps loss.