Molten vault - Boss lava damage

Hello,

In the map molten vault, during the fight against Gulzal the living furnace, the lava covering the ground has a weird damage scaling.

During the campaign on normal, it hurts but you can react and get out in time if you have enough resistances and you use a flask.
During campaign in cruel (before 0.3), and during mapping, the lava always one shot in 1 tick, whatever your resistances/life pool is.

It seems like the scaling is bugged, or is it deliberate that the lava straight up one shot everyone?