The zerg at Tequatl is the majority of the damage that is done to him. However, it is important to remember that since you can not crit Teq, Berserker's gear is totally pointless. The biggest things for the zerg to remember are might stacking, double damage, gear, never party up, and placement.
The best gear stats for the zerg are Soldier's if you do not do condition damage, or Dire if you do. If you are a Guardian, Cleric's is also an option as it can greatly help to keep the zerg alive.
Might stacking is used to, well, stack might. At the max 25 stacks, it gives a 25% bonus to damage per hit. This adds up really fast. The best way to stack might is to not be in a party (which is why the zerg should never party, excluding ERT) and use blast field combos. This works with a combination of fire fields and blast finishers.
Double damage is exactly what it sounds like. Teq has a "sweetspot" where your attacks hit twice, and inflict double damage. You remember might stacking? Pair that with double damage, or DD, and you are going to be doing a total of 50% extra damage per hit. This only happens in one spot, so as soon as you find it remember to call out "DD" in say chat. Not map chat. If you post it in local/say, the rest of the zerg can see the placement for it.
The last thing for the zerg to remember is the placement of items. Warrior banners should go to the left of the zerg, and Elementalist weapons should go to the right. This keeps it organized and makes it easier to pick weapons up. The ele weapons are extremely effective against Tequatl, and should NEVER be overlooked.
Also, remember to stack super tight on the commander. This makes cleansing the zerg infinite times easier for South Turrets, which means more people stay alive, more damage, more might, etc.
