That's the trip I'm taking next week! Only diving in St. Lucia, but considering last minute (if available) in St. Thomas and/or St. Maarten.
If you're interested in St Thomas or St Maarten, I can give you my two cents.
This will be the sixth time I've done this cruise since 2009, and I've always dived in every port, every time. The last time we went was a few months before the hurricane it (which was Fall 2017, IIRC.) And it seems the hurricane really did a number on St Thomas and St Maarten.
For all previous times, we used Blue Island Divers in St Thomas and they were outstanding... great boat, small group, great service, great people. But last time we found out that BID had been taken over by another shop (I forget the name...) and things changed a little. They were okay, but that's all.
I went to look up St Thomas shops for this trip and it seems that shop has now disappeared. So I had to start from scratch. I booked with JJ Divers. They were a little pricey ($130 for a two-tank trip), but I liked their website... all the info I needed was right there. Gave the impression they have their act together, which I assume will translate to how they run their boat too.
St Maarten... oy vey. We've used Scuba Fun in the past, and they were always great. Their shop was (maybe still is?) a short walk down the street from the cruise ship pier (less than 10 minute walk.) But their website is still where it was when the hurricane hit. And I couldn't get a response from them. They message on the site is that their boats were destroyed and they'll try to get up and running again as soon as possible. But it might have never happened.
So this time we're booked with Dive Sint Maarten, which is practically right next door to where Scuba Fun was (i.e. short walk from the ship.) Communication was a bit challenging with them, but from everything I've read (reviews on Tripadvisor, etc) they are top notch where it matters... on the boat.
Basically what I found on both islands is that there seems to be far fewer dive ops now than there were before the hurricane. I't seems a lot of boats were wrecked and plenty of dive ops simply threw in towel, while just a few had the resources necessary to keep going.