Directly in front of the entrance there is a buttress which can be used like a ramp to climb up to the first floor, that offers a good view of the entire room allowing for more direct lines of fire. On the first floor there is also a staircase to the second floor, and the staircase itself is also useful for getting out of the line of fire. Sniping Deadlift from the floor of the arena, or from an elevated position, will complete the challenge, and while sniper rifles are generally unavailable this early in Normal Mode, there is one available as a mission reward for Tales from Elpis.