What's a normal response delay for a paragliding vario?
That is probably normal.  I notice a similar delay when flying with my Brauniger IQ Comp vario (lately mainly in sailplanes.)  Minimizing the delay is why the latest varios incorporate accelerometers as well as barometric pressure sensors.  Sounds like you've already checked the manual to see if there is some way you can decrease the interval of averaging, upon which the primary visual display and audio tone are based.  That adjustment is definitely possible with some variometers produced for hang gliding / paragliding use, but not with all.
Another way to get a quicker response time is to buy a vario that is even older.  For example, check out the &quot;Litek Hummingbird&quot;.