To clear up the haste confusion:
Steady Shot with Quiver Haste
2.0 sec / 1.15 (15%) = 1.74 sec
Steady Shot with Quiver & Serpent's Swiftness Haste
2.0 sec / 1.15 (15%) * 1.20 (20%)
becomes
2.0 sec / 1.38 (38%) = 1.45 sec
BM is still below 1.5 sec cast time on Steady, so haste will not have as much benefit, as
Aerynlore said although their numbers were slightly off.
Unbuffed Marks will need...
1.5 sec = 2.0 sec / 1.15 (15%) * X (X%)
Let's bust out those algebra skills. Oh god, they're rusty. I'm probably going to do it wrong.
1.5 = 2 / 1.15X
Multiply both sides by 1.15X
1.725X = 2
Divide both sides by 1.725
X = ~1.15942
Is that right? Lemme see... Going back to the former equation:
1.5 sec = 2.0 sec / 1.15 (15%) * X (X%)
Insert the value
1.5 sec = 2.0 sec / 1.15 (15%) * ~1.15942 (15.942%)
becomes
1.5 sec = 2.0 sec / ~1.3333 (~33.33%)
... /facepalm... Duh. I guess that is right.
So if nothing here is inherently flawed, to get 15.942% haste you will need...
15.942 * 32.78998947 = ~522.738
Tada! Verified, the point at which haste stops being as good for non-BM hunters, unbuffed of course. /bow
Presumably what
ElginRoko said about needing 412 rating after the 3% haste buff from a boomkin or ret paladin is true as well.