2,807 in 6 months, compared to 2,034 by sea in 2014. Should come as no surprise actually, the Embraer 190 only comes once a week and with 95 seats that makes just under 2,500 if at 100% load factor, it's probably quite a bit less. Once a month it goes on to Ascension and back, principally for the Saints working there to go to/fro, which will add to the figures.
You do indeed have to question the oversize terminal. From casual views the building looks larger than the terminal at London City, which processes that number of arrivals in a two hours. A couple of Portakabins would have surely sufficed.