I don't know if anyone is still interested in this thread, but I do have something new: How to handle Head On at minimum range.

Stand at the left or right edge, and move back as far as possible without getting Connectivity. When the cast bar finishes, move as close to the boss as possible. The game registers your distance for the damage at the end of the cast, not the actual hit, so this trick can help minimise the damage.

Still need cooldowns for it, but this is probably the least talked about mechanic, and yet causes the most MT grief in this fight.