Imo pressure has nothing to do with how good or bad a water might fish. What does have a huge influence is the weather conditions that low and high pressure systems bring.
In summer high pressure usually brings high temps with no wind - conditions that tend to see carp sunbathing rather than feeding. Low pressure systems (in summer) tend to bring big winds, overcast days and rain - perfect for getting the carp feeding.
In winter high pressure can be good - it normally brings bright sunny periods which provide the warmth the carp crave at this time of year. Zigs can be a killer in this situation as they're on the move in the upper layers. Low pressure can still be great depending on temps.
Some guys believe that pressure will dictate there the carp are in the water column (i.e. in high pressure they'll be up in the water and in low pressure they'll be on the deck). This is a load of tosh. The carp will be up in the water when they need warmth and it's sunny (which normally coincides with high pressure) and they'll be on the deck to feed (which normally happens when the conditions get them moving (big winds, overcast skies).
Of course, these conditions are not always guaranteed. It can rain during periods of high pressure and it can be bright during periods of low pressure. Hence, the pressure itself has very little influence.