This is not me saying GoHB is required, nor is it me saying that GoHB is superior to Glyph of Frost Strike on single-target enemies. This is just why I use it and I hope that it will be of benefit/use/information to other DKs that may find themselves following the same progression path I have.
As a DW Frost, and probably 2h Frost, you have two mandatory glyphs. Glyph of Obliterate and Glyph of Icy Touch, for your third glyph though you can either go with Glyph of Howling Blast or Glyph of Frost Strike. GoFS is the superior glyph for fighting bosses or single targets, however there are reasons you may want to go with GoHB instead.
Here are mine:
Most trash will not live beyond 20s or so, if that. Which means you actually lose dps on a pack of mobs when you do PS->IT->Pes->HB, compared to HB->OB-rime->HB, or even if you have to wait 6s for a HB to come off CD.
Next is if you're responsible for ITT, it's far easier to maintain that buff using free HB to keep up your FF than having to constantly refresh it with IT, as well as it then frees up another Obliterate and makes it easier to keep up your blood plague with a death rune.
Third thing is that a lot of folks say "HB hits like a wet noodle when you don't have your diseases up!" Which is false. It hits for 20% less, yes. However that's not a very big difference in power or overal dps over the life of a fight considering how with GoHB your FF at the very least will never drop off your target - even if all you're using are rime procs.
GoHB provides massive hits right from the get-go. This burst damage gives DW frost a lot of momentum that they can carry into the rest of the fight. It relieves a lot of the ramp-up time since you can just HB->Ob->BS->BS->FS->OB. Moving your heavy hitters faster up the line for quick fights.
It also applies your diseases to multiple ads in a harder hitting fashion than pestilince, which makes a pretty big difference when you are fighting things that have low health.
So if you find yourself in a gearing situation that leads you more into heroics than raids and other situations where the trash dies fast, and you make sure to prioritize HB on large groups of enemies and whenever you get a rime proc having the GoHB provides much better returns.
It also helps promote a more priority based rotation since you aren't as required to constantly reserve two GCDs for IT & PS.
Oh and if you are moving through trash and can get to the next group before the rime proc goes away you can apply FF for free to the entire group.
So that's my feelings on that. Hope it helps some folks.