Rangers are already limited a lot on where you can fight - you can do decent outside the wilds but you're playing at a disadvantage.
Mariners get absolutely jacked outside of the water, and how many people actually even go to the water these days? Nexuns are getting fairly non-existent, you have several options besides spirits for ranking, and in the midranks where a mariner could be scary... you want to sit on the ocean for hours at a time hoping someone shows up?
I'd argue that a mariner is the most restricted and boring class in the game... even a water shifter has a better time.