Hi Alexander
In my humble opinion an RDA will always provide slightly better flavor versus an RTA. About half my setups in rotation are RDA's.
In this first video Jim has his coil placed higher than yours. He likely prefers more throat hit. He is using more wick than you are on the tails and did not trim any cotton from his tails.
In this video Todd has his coil about where yours is and he is also using more cotton.
Just click "Watch on YouTube" to play Todd's video.
Both say they are getting excellent flavor and both say it performs best at higher wattages. Jim starts at 35w and then bumps it up to 42.5w. You're running it up to 55w so that should be fine.
I would try wicking your GT V as they did without trimming any cotton off the tails. Also make sure the density of your wick is not too tight in the coil. Too tight in your coil can mute flavor.
The GT V ships with two 3x1.8mm air disks installed. Only other thing I can think of is to try a set of the more restricted air disks. Like the 3x1.5mm or even the 3x1.2mm.
Good luck!!!