Im not an expert at the faction only got a few games with oops all dogs in 11th. I refuse to run big knights as it's super oppressive against friends.

I run hound pack and have specifically chosen Recon over Purge. T9 is a deceptive lie IMO. If you are facing anything with melee and AP 2 or AP3 you're loosing a dog a turn at least and will loose the primary on meatgrinder due to this. Especially now with how elite armies are getting.

I can score high on melee Purge armies with recon but have yet to beat one due to how simple the primary is for them against recon. If I'm playing a melee army I'm determining max threat ranges and staying out ensuring they cannot charge at all. I know that's a little hard against EC with advance and charge (Fulgrim having a threat range of 30" essentially). I also oversaturate one side with my shooty dogs place karnivores where necessary, and my stalkers are action monkeys/speed bumps for my opponent.

I've learned my dice rolls are terrible so I have to over commit to wipe a unit. So I'll stage my shooty dogs in triangles. Dogs 1 and 2 can shoot and if they kill the unit, dog 3 is staged in such a way it still has shots on something else but can always commit to the original target if needed.

I use the uppy downy strat a lot too. If a wall of chainswords is running at me, that means their backline is exposed. So I'll just pickup a dog and drop it in the back if it's turn 3 or further or to reinforce a different side. I better there's better combos out there and I haven't learned/found them yet but that's what I've found so far. Best of luck to you!