This is just your subjective opinion. And game mechanics discussion isn't about how YOU feel what makes the game fun or not.
You repeatedly use "FUN" in a game mechanics discussion on every forum in every thread, why?
From MY subjective opinion, I find zerging and WS at 1000 TP is more fun due to DPS job can compete with each other. And DDs having parse war against each other is the only competitive element in this game as it stands. Since this game has no PVP, nor HNM camping anymore, the it's the only competitive element in game. And some players such as myself find competitive element in a video game fun.
That being said, just because I find zerging more fun, I don't use it as a reason to agree/disagree against a game design mechanics.
At this point zerging with super buffed 5 DD generates more DPS than 2 DPS SCing in many situations. I advocate such setup not because I personally find fun, but because it's mathematically stronger.
Even if you want to advocate 2 DD SCing with each other because YOU think it's fun, it doesn't really apply to everyone because it's YOUR personal opinion.
tl;dr, your argument about inundation being very useful is invalid. It has some uses in game, but not all the time. And it's not enough to make RDM less niche than it currently is.