If you own Epson and are in the U.S. you are using Decision One for warranty and or post warranty work. There is no other solution unless you want to attempt the repair yourself. Not too hard on the 9600 gen and 7800 gen printers, but on the 9900 it's a much bigger deal as Epson definitely made so you have to have their program to re-calibrate the printer. The head technology on the 9900 family is much more involved than the older machines, plus you can take a 7800 apart pretty easy, the 9900 is way more complicated.
I have used D1 now for over 6 years all based in LR Arkansas. I have had the same tech for 4 of those 6 years, he understands my environment, trusts my opinion on the problem and orders the parts. I have yet to have a single problem from a repair. The 9900 has been around for a long time, and the newer 9890 is based on that same setup, so most D1 techs should have had experience on them.
I know for a fact that their current focus in on the Epson solvent lineup as there have been a lot more current products announced and the trend in the bigger shops, signage, etc. is to move to solvent.
Not saying D1 is perfect by any means, but in my location they get the job done. When I have had problem with a repair they have always fixed the issue, even on a printer out of warranty and no longer on extended warranty. If you feel your tech is not qualified, then you need to call Epson and have them dispatch a call to the D1 field manager. That person should take the lead and both call you and get a qualified person out to your printer. I understand that if you live on an island as the OP does, this may be a bit harder to do.
Paul Caldwell