Agathelos the Raging

Boar pens and bat caves
Beyond Ramtusk, clear the Death's Head Seer and Ward Guardians that keep Agathelos sealed before engaging the boar. Continue through the bat caves afterward for Kraul Guano if Going, Going, Guano! is in your quest log. Keep the healer behind the bat pull so a nearby silence does not stop recovery after a stun.

Agathelos the Raging
Elite BeastAgathelos combines Rushing Charge with Rampage's nearby stun, so losing melee contact and crowding the healer into the boar create different risks.
Abilities

Rushing Charge
The tank should keep Agathelos within melee reach instead of letting the boar rush across the pen for an empowered opening attack.

Rampage
Keep the healer outside Rampage's nearby damage and stun so healing remains available to the frontline.
Tank- Clear the Seer and Ward Guardians before engaging Agathelos. Keep melee contact and use defensive abilities before a low-health situation becomes a Rampage stun; avoid retreating across the pen and inviting Rushing Charge.
Healer- Heal from outside Rampage's nearby stun. Keep the tank healthy enough to survive being stunned rather than joining the melee stack beside the boar.
Damage- Let the tank establish control before committing damage. Avoid taking threat and running across the pen, which leaves Agathelos chasing a new target with Rushing Charge; melee should watch for Rampage pressure instead of drawing the healer closer.