Switching printers is not advised, it is not causing your color problems.
With JPSS your results should look like this. I use Cobra pigment inks and a WF1100 (4 color) but the inks are a very good clone of Epsons in terms of color. I used a C88+ in the past with Epsons Durabrite+ factory inks and got similar good results.
You mention "with Durabrite inks", how on earth did you get "Durabrite" inks into a CIS? Durabrite+ inks are what's in the Epson OEM carts and is Epsons trademark. What inks are you really using?
Your issues relate to color management (or lack thereof), inks and/or printer settings and inks. I use matte paper settings in the Epson driver.
The top transfer on the tshirt is using a color profile, the lower transfer is without, the profile makes it "pop" more but the lower image is more color accurate.
To put it simply, you are doing something wrong.
Before heat transferring this is normal!
The inks very quickly get absorbed into the transfer layers by design. They don't sit in the top of the sheet, they are absorbed into the paper. This is not inkjet photo paper where the inks stay on top!
After you transfer the image should appear normal.