Tampa here: sounds like all flights out of Florida are about the same; best to look for a way to get direct to STT and then ferry. That is what we usually do. Have a land based trip coming up late May and doing a whole bunch of options because of Jet Blue Credit. Flying out of Tampa non stop to stt then ferry to Tortola. On the way home intercaribe out of EIS to SJU then another Jet blue from SJU to Tampa. Pretty easy except heard nightmares regarding both Intercarib and silver airways. They are the most inexpensive ones from EIS to SJU.
Sometimes in the past I would pay a little more at least one way and do a cheapo way either there or back.
Just looked at the AA flight options from Tampa to EIS and now looks like they stop in SJU and then use Silver to continue on to EIS and there is only one flight that is not 16hrs long

$1920RT for 2ppl. Also checked AA straight from MIA and they only have one flight under 15hrs and still stops in SJU and then uses silver onward to EIS $1710RT!. Both of these were for early November. Looks like the AA thing is not working out too well at least from Florida.