1st: Dont stop at 1400 haste ... no matter that your Haunt and UA will go under 1 sec, your SB and Corruption (your main DMG spells) benefit from it even when you go under 1 sec cast time of Haunt and UA!
2nd: As they said all your DoTs except Corruption will automaticaly get the % bonuses when they proc, but Corruption needs to be recast to get it (but Corr will keep it till you let it fall of or recast it, while the other spells will loose it the moment the proc is gone). So you need to recast your Corr at least 1 time (when Death's Embrace comes in play, aka under 25% HP, and you have DM proc from the first tick of your UA and a proc when DE is active) or 2 if you dont have the luck of instant proc of DM (1 time when the DM procs and 1 time when DE comes in play).
3rd: Dont spec in Nightfall at all ... in my last test I lost 50%+ instant SB couz of the bug everyone is talking about! Its a DPS loss!
4th: The Fellhunter's Bite works fine (FH's normal DMG is garbage, but the bite works as intended), critting for 6k+ when I have most of my procs active!