They make more of an impression when they don't appear every season.
Season 6 was a good break.
In general, they need to change the dalek design for them to be fresh again.
I get that didn't go over well when they changed the design in season 5, but they've been using the same one since season 1 (of the new series).
(They also need to kill people whenever they make an appearance so they can be taken somewhat seriously, as morbid as that may sound)