Are Diablo's abilities predictable?

Question

Diablo has a number of attacks, some are extremely deadly at close range. Although he has an obvious "charge-up" animation for most abilities, some are very short.

Does Diablo react based on the player(s) actions (e.g. proximity to Diablo or to each other, use of abilties, etc) or is he purely just a dice rolling fire and bone hate generator?

Answer 1

Playing with Diablo in Normal Mode - note that these may change in higher difficulties, but I can't just sit there with Galvanizing Ward and tank Hell Diablo forever to be sure.

Most things seem to be quite random - though I suspect there might be a timer on bone cages - however, there are a few cases governing when he uses certain skills.

Phase 1

• Diablo never uses either of his fire attacks at melee range - though occasionally he runs away after a string of melee attacks, and then often uses the 360 degree fireballs before closing back in.
• The fire patch only seems to be used at mid range if Diablo's having a hard time closing with you to melee.

Phase 2

• Shadow Clones spawn at the beginning of the phase, at 66%, and at 33%.
• Unlike Phase 1, Shadow Diablo LOVES using the fire patch in melee and after he runs away - but he'll never use one while one is out on the field.

Phase 3

• His love for fire patching the melee sticks around. And now he 360 fireballs in melee, too. And his energy breath. AND he doesn't care if multiple fire patches are in one place - I watched him use it four times in a row. At this point, I don't think there's any rhyme or reason to how he acts, aside from 'extremely dangerously'.