EXCELLENT ac repairman on stx??

Replace it. I had a Mitsubishi split unit system as well that was a complete lemon. Had to call a repairman every 6 months or more. It was a expensive unit as well. I replaced it with a cheaper Frigidaire unit from PriceSmart and haven't had a problem since.
If you lived on STT, I could recommend someone.

Replace it.

That was my first reaction. If you've already had "several" repairmen tinkering with it to no avail then it probably needs to be replaced before you sink any more money into it.

Can't say as I disagree about getting a new one. That said, Quality Electric Supply, Inc. is a distributor for Mitsubishi -- which require some specialized knowledge/boards for their splits. On their site they say "Quality Electric Supply’s staff and engineers formed an alliance with Mitsubishi Electric and certified installers. This alliance makes the absolute best support team in the islands. Your support team consists of manufacturing experts, design, sales, and implementation engineers as well as customer service specialists." We have used them for other, larger, projects--although our splits have not required service yet. I'd ask them what they would recommend.

As I search for homes on St. Croix online. I look at all the photos of the houses seems like all the A/C is done by window shakers and ductless splits. There really isn't a more inefficient way of cooling. Not to mention everything is crammed so tightly into those units they're near impossible to work on. The same size unit used to cool a single room could probably cool an entire wing if not your entire home if it was centralized. I have 1.5 ton for my home in the states. We've had consecutive days over 100 and lows in upper 70s and my 1200 square foot home stayed 78 with low humidity. Once on the island I'm going to amerce myself in alternative power and energy efficient solutions

To answer the question on your split unit. It's more than likely not that the people don't know what they're doing. If I were to guess, I'd guess you had a burn out. Even if the mechanic properly flushed the lines there is still contaminates in the system. Those contaminates in the system get lodged in orifices and fill up the filter dryer. You should just replace it.

If I lived somewhere that electricity didn't cost as much as it does here I'd have a central air system. Friends and family in FL pay around $60 - $80 a month for running their units 24/7. Not the case here.