i'm not sure why people are trying to say thorium headed arrows aren't worth it. they're 4.5 DPS above jaggeds, and that's just on autoshot. if you do 200 autoshot dps with jagged, you're doing 204.5 with thorium - that's over a 2% increase, and it benefits your specials as well. i use thoriums throughout every naxx clear.
Yes, but overall they're less than 2%. With a crossbow of smiting, you get 5 shots per 10 seconds, or 1 shot per 2 seconds, for a general average high DPS of 500 (just saving time, here - I think most will accept that if a hunter is doing 500 DPS they're doing well). To that 500 DPS you're adding 15.3 damage/2 seconds = 7.65 DPS, or right around 1.5%. That's all well and good, but on my server thorium costs 40 silver per bar, and a single stack of thorium arrows will run you a gold. That's 11 times the cost of jagged arrows (12.5 if you're seargant or above).
Why on earth would I spend that much extra money on trash or bosses where total DPS isn't important, for such a tiny increase in overall damage? Seriously, 12 times the cost for a 1.5% increase in performance?
In the same vein, would you use Brilliant Mana Oils instead of Lesser Mana Oils? They're signifigantly better, paired, but they're hideously more expensive.