Well the charters have been operating long flights at minimal legroom for years and hasn't caused any problems on the type of routes EASYJET will fly these aircraft on. Seat pitch of 28" is widely regarded by A and B as safe and is deemed safe and legal by the authorities. In fact some TATL charters by Finnair have been operated by 28" pitched cabins.
As mentioned a small proportion will be 28", most will be the same as British Airways A320's at 29" or 30". For those who need or prefer extra legroom seats they can be purchased. Some seats on the current fleet are 28" and I've never been made aware of any health issues caused by that.
As with all things you have a choice. If the product or offering of one airline doesn't fit your demands and needs fly another airline.