LMB - Fetish Army (Legion of Daggers) - pets, pets, and more pets - can't get enough!
RMB - Piranhas (Bogadile) - HUGE burst damage on a relatively low cooldown
1 - Big Bad Voodoo (Slam Dance) - Offers a huge increase in overall damage and attack speed, causing the fetishes and gargantuan to really hammer Ghom down quickly.
2 - Zombie Dogs (Rabid Dogs) [Using Tall Man's Finger] - With the use of TMF, this dog crits insanely high, and its poison DoT is also increased. In conjunction with BBV (1), it offers an insane DPS increase.
3 - Mass Confusion (Paranoia) - Trinity is smart enough to use this after approaching Ghom, causing the boss to take a huge chunk more damage, so it's used for obvious reasons.
4 - Gargantuan (Wrathful Protector) - This guy's just a hard hitting son of a bitch, and it lasts for 15 seconds, which is usually more than 3x more time than what is needed. He hits for outrageous numbers, especially in conjunction with BBV and Mass Confusion.
Passive 1 - Fetish Sycophants - Even though with Fetish Army, this passive is slightly less useful, it's always nice to have the additional support of extra fetishes after Piranhas do some damage on the field. There may be a better option, but I have not found one.
Passive 2 - Midnight Feast - This passive greatly increases the damage from your Zombie Dog(s) and Gargantuan, and is highly recommended.
Passive 3 - Jungle Fortitude - I use this in place of Grave Injustice (my usual passive), just because I don't need the CDR on a boss farm, and the extra toughness helps keep movement to a minimum.
Passive 4 - Pierce the Veil - 20% bonus damage. 'Nuff said.
Here is how I have my Paragon allocated, at 276 Paragon: