[SPOILER]At first i was having so much trouble defeating the hellhound. I'm on normal difficulty and i only require to spend just 1 bronze point in Strength to defeat the beast.
The key in defeating the hound is the aard sign and you must RUN!. My strategy is to use the group style and kill all the weak barghest first then confront the beast. Killing the barghest will be very much easy. When the hound get close use the aard sign and knockdown it. When confront the hound use the strong style. Once it's knocked down, confront it and try getting a couple of hits.
When your health is running low, RUN!!. This is the most important thing i guess most people miss. Use the OTS (Over The Shoulder mode) and run around avoiding the hound (it can't manage to chase you). This will both grants Abigail (considering if you have her on your side) to heal you and to regen your endurance (for the aard sign). Once you are healed and endurance regened, confront the hound and knocks it down and use your strong style against it.
Rinse and repeat and i just used only 1 bronze point in strength (23 points unused) to defeat the hound. In the process, remember to drink Blizzard and Tawny Oil. I think most importantly is RUN. Remember it