yorktown1983: you mean you put the axii ability in one of the 3 open slots you have right? cuz theyre not there in that screenshot and that would explain it
dawhicher: I see what you mean... I never had to equip that skill the first time it was used in a dialogue though so I was expecting it to work that way. Thanks for all the replies!
There are some axii options that don't require the skill to be equipped (I can't remember if it's only one, or more off the top of my head as I'm now 100 hours in to the game), the vast majority do require it to be equipped however :)