I just started a new game a few days ago and beelined for the docks to buy the dog. I figured if I got him early and raised it up around the same level he'd be a lot stronger than getting him at level 15+ and the dog being level 1. The stat growths are terrible, are they randomized? if so the % would have to be extremely low, because at level 23 he's gained maybe 2 defense. He can tank 1 hit from a crocodile that does around 34 damage and survive with 1hp. He attacks randomly, so it's not a huge benefit if you did the master quest and can 1 shot most things. The dog is just a bit underwhelming is all. I still haven't gotten the imp this playthrough, but I am betting it will end up outclassing the dog, because of more armor options and the use of magic.
I forgot how so many quests are wrapped up in progress with something else. Like if you never take the stables girl out, you never advance Erevi and in order to take the stables girl out you have to advance Erevi to a certain point, then do all the Qetesh stuff with Ziva that you can and then after Gabriel helps you, only then can you take out the stables girl and then you can also advance Mia's stuff.
On a sidenote Tinkerer is a genius when it comes to money shots, his sex scenes too are really good. There is a lot of visual detail that just doesn't exist in many other games. Here he is diligently handcrafting every droplet of spooge and squirt and most games just ignore that altogether.
