Okay, so I'm a completely new player, my highest level character is level 20. The only useful stuff I can write is for other newbies. Anyway, this post should answer the question: "Is it worth rushing Hunting Mastery for Scatter Shot?"
With a grand total of two blue items to my name and very little knowledge of the game, I tried not putting any points into any other skills until I got to Scatter Shot.
How slow was it? Was it frustrating? How many times did I die? Was it worth it?
Level 1 - Bought a bow from the merchant. Oak crude bow or something like that. Meh.
Level 2 - First mastery... Hunting! All points went into Hunting Mastery, no points in skills.
Level 3 - Two more points in Hunting Mastery, and one in Marksmanship. It's a prerequisite for Scatter Shot, so I may as well benefit from it now.
Level 6 - Still no points in any skills. Man.... this is slow and boring. At least with a bow, you can use hit and run tactics so survivability is not a problem.
Level 11 - Still no points in any skills. Getting rather annoyed by the slow killing speed. No deaths yet so I'm glad that survivability is still not a problem. No deaths yet. Zzzzzzz.
Level 12 - Finally, I have 32 points in Hunting Mastery and put my first point into Scatter Shot! I went out to the wilderness to try it out and... WTF?!? The improvement in killing speed was almost negligible. I can't believe that I waited this long for such a crappy skill!
Level 13 - Four points in Scatter Shot now. Hmmm... killing speed seems to have improved a little, but the skill is still underwhelming.
Level 14 - Six points in Scatter Shot (I decided to put a point into Puncture Shot as I had a bow with +2 to Puncture Shot). This skill is beginning to show some potential now. Sometimes I'd notice I'd kill two monsters in one shot. Still, it's far from a powerhouse though.
Level 15 - Nine points in Scatter Shot. I'm beginning to like this skill. I'm 1-hit-killing most monsters, and killing two or three in one shot was a fairly regular occurence.
Level 16 - 12 points in Scatter Shot. Now we're talking! Fired into small packs, killing two or three monsters at once is the norm now. I knew the wait would be worth it!
From there, I felt that power was plentiful so I went about increasing Wood Lore for the attack speed instead of Volley as recommended. But go your own way... Volley definitely gives more power if you don't mind the attack speed. By level 18, it was pure pwnage! And by the way, still no deaths.
So, for the new players thinking of starting a bow Hunter untwinked, you now know what to expect when the veterans tell you that "hunters start off slowly". It is quite slow and frustrating until level 15 or 16, which represents around 10 -12 hours (?) of gameplay, but the result is definitely worth it!