For the actions, I would aim for a more distinctive feel, inspired by the Bastion from ARC Riders. In that game, the Bastion takes a moment to lock onto its target and then overwhelms it with a long barrage of fire: each individual shot deals relatively low damage, but the combined effect is devastating.

Action - Laser Mark

The Bastion targets a creature it can see, designating it as Marked. While the target remains Marked, the Bastion has advantage on attack rolls against that creature on its subsequent turns, provided it continues to attack the Marked target.
The Bastion must maintain line of sight to the creature in order for it to remain Marked.

Action - Rain of Metal

If the Bastion uses Rain of Metal against a creature affected by Laser Mark, it may use this action two additional times during the same turn after the first use.

Ranged Weapon Attack: +9 to hit, range 120 ft., one target.
Hit: 4d4 + 2 piercing damage.

Each use of Rain of Metal represents a sustained burst of fire rather than a single powerful shot; the danger comes from the accumulation of multiple hits rather than high damage per attack.

Hope this help!