I notice alot when i use jackhammer in a group of adds all i see are words (immune, immune,immune) no damage is being done and my aftershock doesn't seem to be working when this happen At first i thought it was because a earth dps was in the raid and he used jack hammer but im also getting immune in alerts, solos and duos. Is this on purpose or a bug????????????????
You do damage the mobs are just immune to knockdown you don't have it all time because knock is only when mobs are dazed. You just don't see damage because they are hide by the text but you do damage.
The Immune message is most likely Immunity to Crowd Control or other Effects not damage. You should see damage numbers in your Combat log even when they do not appear as flying text.
I have a similar problem with my Gadget dps. Using any power (not weapon attacks), I see "immune" dropping instead of numbers like ~70% of the time. What's up with that??