Couple of points Matt - I haven't looked at comparable points costs though.
Warriors/Chosen - I would keep Warriors and Chosen as separate entries, much like Skeletons and Revenants. Factor the extra cost into Chosen. Maybe make Warriors size 10/20/30, and cap Chosen at 5/10/20, much like Dwarf Berserkers or Elven Palace Guard.
SPD should be 5. Melee 4+ and Def 5+ seems fine, maybe give them the Abyssal Dwarf option of replacing Shields with two-handed weapons for free, making the CS(1) and Def 4+?
Bump Chosen to 3+ Melee and ramp up the points.
Tribesmen - Seem fine. Wary of the 4+ Melee though, especially for a cheap unit.
Forsaken - seem quite nasty.
Knights look about right.
Warhounds - should probably be DEF 3+, same as Ghouls/Zombies, they aren't really armoured or especially tough. Don't know if I'd go with 10 model units, just to stop Hound Spam.
Trolls - Should probably be CS(2), moreso than Forsaken.
Heroes/Monsters - Spd 5 for the Chaos Warriors, the Exalted should prob be a bit more costly compared to a Dwarf Berserker Lord, SPD 5 and approx 180 I reckon, going by the extra SPD, DEF, generic Inspiring, and Elite rules. Also, don't know if Heal really fits into this list.
I like the Whim of the Gods rules. Another option would be along the lines of 'Under the eyes of the Gods' whereby Heroes with Inspiring have a range of 12", to represent the mortals fighting harder under the gaze of their champions.
Hellcannon - look at the Abyssal Dwarf warmachines, but consider classing it as a monster so that it can charge/doesn't take triple attacks in CC.
Ok, Magic power... Spells...
How about having the standard Undivided Sorcerer as is, but allowing them to be Marked for, say 30 points?
Tzeentch Sorcerer - Flickering Fire - Zap, but Piercing (2)
Nurgle Sorcerer - Stream of Corruption (n) - Breath Attack, with Piercing (1)
Slaanesh Sorcerer - Languid Advance (n) - Dark Surge with no Shambling prerequisite.
Just a few things to consider/abuse.