Yeah sorry I was a bit muddled and rambling.
So basically Hellhounds and Griffons are not tier one units in most Guard builds due to their more specialized uses, harder to have synergy stats, and in general, there being just better bang-for-the-buck upgrades/other formations to have in your list (e.g. Hydras), especially at 3k. So when I say it's a faction wide issue, it's really one just having better toys to take instead.
In the Cadian list they're somewhat usable as a 6 strong formation as they can lose a unit and still do something so they're somewhat unique as a formation (everywhere else they're an upgrade IIRC). The real issue is that for the points in an all-comers build there's just better stuff you'd need instead. Now in my experience they can work out in Cadians as the follow up to an attack or as a supporting / preping unit for a Cadian Armoured Fist formation as all have 30cm movement and that and gives the list some much needed mobility since the core formation is a slow, hard as nails WE+infantry force.
Typically I'd use them for digging some enemy infantry out of cover as you can move right up with the hellhounds, prep and try and burn them out with the 6 Ignore Cover shots and then retain and assault with the mechanized infantry and get the 6 additional 3+ FF shots. That's going to put some hurt out.
Something similar can be done with griffons but instead of being a support fire formation you can use them to advance far into cover and use them to sustain with shells over another unit and cover via Indirect at anyone stupid enough to come near. Worse case you're enemy has to expend a few activations to go shift them and maybe that's the move that gives you the chance to set tempo. However that's all theory hammer and I have not been able to use them to their full effect, probably due to my inabilities as a commander.
When they seem to come into their own in my games have been when we're doing some serious city-fights where cover is abundant and range is reduced (Stalingrad) as opposed to rolling hills and rivers and forests (Kursk).

_________________
He's a lawyer and a super-villian. That's like having a shark with a bazooka!
-
I HAVE NO POINT-
Penal Legion-Fan list-
Help me make Whitescars not suck!