As you have clearly said people have different ways for doing this fight but I'll do my best to describe how our group clears HM Toth and Zorn. Everything is in terms of Republic classes because that's what I know best.
Ideal Group Composition:
Two tanks (preferably a mix, ie. not two Vanguards)
Two healers - One Sage on Toth tank, One Commando/Scoundrel on Zorn tank
Two Melee DPS - Preferably Two Sentinels on Toth
Two Ranged DPS - Preferably One Gunslinger and One Sage
Our healers and ranged head to the far side of the area (cave entrance side) and then the two tanks pull Toth and Zorn to the walls. When Toth leaps to Zorn, we have the tanks swap positions and keep the bosses in their respective spots. This is less confusing for our group and it helps prevent dragging the boss's AOEs in range of our ranged DPS. If a ranged DPS acquires Fearful have a melee swap bosses. Also have melee and the tank on Toth CD through his frenzy to help the healer out. An important part is to keep Melee DPS to the cave side of the boss in order to stay out of Toth's Fearful leap. We usually have trouble balancing DPS as melee can still maintain most of their DPS during the spike phases rather than the range who have to run around and dodge them at a far while staying out of the fearful leap to come.
Sorry if this written a bit messy but I'm quite tired at the moment.