The problem is eventually there is almost nowhere to go to avoid damage. It's easier for ranged classes because they can dps and stay away from centre, so when they catch the AOE they take it farther from it then melee dps who have to be near the boss to be able to perform their job.
Regardless melee have ZERO issue when they have a competent tank. The tank just needs to move the droid away from the AoE and problem solved. I've noticed people complain that this sometimes means moving through the lava, but if your healer is doing their job then that's also a non-issue (it's only a couple of seconds to get into the closest safe zone). Frequently people struggle with this fight as a result of sub-standard healing.