Team against Rayquaza ancient power

"Still, I am hesitating whether I should use Golem instead of Aggrons for more dps?"

Yes, you should. Aggron is amazingly tanky but really its DPS is quite low. Golem is a very good compromise of survivability against AP and high DPS.

Stick to Aggron/Gardevoir in large groups where individual damage bonuses are improbable to save potions and switch to Golem in smaller ones.

Other than jynx all others can tank 1 AP and a few DT, which means dodging at least 1 AP should be safe and easy. I will not change anything unless partly cloudy weather.

Piloswine - Golem - Golem - Golem - Golem - Golem.

Piloswine is neutral to rock, and deals ice damage (ideally).

Golem resists rock, and does double rock damage which Rayquaza is weak to. Pretty simple.

Also note that on partially cloudy days, Golem is the second best counter (after Articuno), regardless of moveset, just like Gardevoir is the second best counter on cloudy days.