So with your first post you give us a pointless list of wishes you have for a class. Sweet!
My thoughts on tweaks to the affliction tree to simplify and improve it, without necessarily pushing the dps through the roof or making it idiot proof.
Flip Improved Fel Hunter and Nightfall on the tree.
Change Improved Fel Hunter to return part of it's mana to 10raid/party members when Shadow Biting. 0.5% maybe 1%, would have to be balanced for sure.
Change Nightfall to a 1pt talent that makes Shadowbolt an instant cast spell with a 2 second cooldown which would be affected by spell haste.
Change Demonic Power in the Destro tree to also speed up the Fel Hunter's Shadow Bite.
Change Grim Reach to Dark Reach affecting all Shadow Spells, change Destructive Reach to Flame Reach affecting all Fire Spells.
(Saw this one in the thread and liked it.) Increase Haunts damage, but make any mob affected by Haunt immune to your fire spells.
These changes would make the Fel Hunter a viable and worthwhile pet to utilize regularly in groups/raids, even in non-Dark Pact builds. They would make Affliction rotations easier, by eliminating cast time on Shadowbolt which makes keeping Shadow's Embrace up easier and simplifies throwing a filler bolt in when dots are about to fall. The cooldown helps alleviate some of the dps increase a pure instacast Bolt would bring. Of course Glyph of Corruption would have to be modified to compensate. It also eliminates Immolate in deep Affliction builds, simplifying rotation more. And the changes to the Fel Hunter and Nightfall would lead to some interesting Affliction/Destro hybrid builds.