i asked this on one of the quests thread and did not get a reply...

here it is again:

i was fighting Diablo in Normal for the first time (using a DH), and my tactic was kiting him/her with Strafe. sometime around Phase 1, i lost my Strafe, as in the assigned skill number became a blank, and it went on 'till i killed him. after combat, i was able to reassign the skill though (i did not attempt to reassign the skill during combat because i was nervous, facing him for the first time and all).

so i decided to check out videos of other guys going solo against Diablo in Normal (ando ther difficulties), and i noticed that it never happened to them.

is this a bug? or is it one of Diablo's abilities?