Dash Rendar ability reads, "You may ignore obstacles during the Activation phase and when performing actions."

Which means that if he is parked on rock during the combat phase, he can fire! Why this is not the Activation Phase and nor is an attack an action. Am I reading this right?

He can't fire

He just ignore obstacles during the activation phase.

He can still boost barrel roll off the rock and then fire, but cannot fire while parked on a rock

The activation phase you set and reveal your dials and move

Then you can take an action from your action bar or if you have an upgrade like engine upgrade.

Then it's the combat phase

The activation phase is over

Dash Rendar the pilot can't fire in the combat phase if he is overlapping a rock.

Dash Rendar ability reads, "You may ignore obstacles during the Activation phase and when performing actions."

Which means that if he is parked on rock during the combat phase, he can fire! Why this is not the Activation Phase and nor is an attack an action. Am I reading this right?

It sounds like you might have a little confusion between Dash Rendar the pilot and Dash Rendar the crew member. The shooting stuff? That's all Dash Rendar the crew member.

Dash Rendar the pilot? He ignores rocks while he's flying/moving/acting, not shooting.

Dash Rendar the crew card? He's a gunner, and ignores rocks while he's shooting (not flying/moving/acting).

His Pilot ability is excellent for Debris as it only has affects during the activation phase which he ignores.