It was my first thought after hearing it Like a zombie trying to scream and vomitting at the same time...
I assumed that they simply don't want to put additional work in creating better sound for death hounds. Then I met Durzog mobs in Greymoor... They had a beautiful uncanny howl designed for them I'm happy for Durzog mob, but I'm very unhappy for the mount. There was technical work put into the "zombie scream", but aesthetically it sounds disgusting. Not scary, it doesn't compliment the legendary Death Hound creature. While somebody really put their heart into designing the beautiful howl ...for a simple Durzog:

https://youtu.be/ZbxNXCPkEvA

There is still no wolf-based mount with awesome voice, while somebody in designer team is truly capable of creating masterpieces
I always praise the person who has created the voice of Flame Atronach senche - and Durzog howl is on the same level of awesomeness This feels like the howl which belongs to Death Hound. Or howl of the wolf from Nightfall crates, at least

Yeah, the zombie dog pet is just awful and I am so sick of hearing it everywhere.

I wish we had an option to turn off pet sounds in general.