Cenotes Map Boss Went Invisible

Not sure which of these is design, which is bug, but felt unintended

The giant bird boss that casts tornadoes (sorry, the name escapes me) in Cenotes Map.

When he cast his tornado he went invisible. I remember when I played in 0.10 he would fly away, then come back. However in this instance he went completely invisible. The tornado persisted for a few minutes, instantly jumping on top of me when the boss did his pounce like move.

After the tornado finally dissipated the boss remained invisible. I was only able to attack him (as melee) by seeing where his wind attacks originated from, then pouncing and lunar assaulting to chill him. The chill effect then allowed me to see an outline of him. Even after defeat, his corpse remained invisible and the loot just appeared.

On another note, is it possible to shorten the duration of the tornado during the fight? Melee literally can't do anything besides run around for a few minutes.