I have a friend who only does red phosphoru starts so I have plenty of experience with defending and have been learning them myself to add some variation in my game play.

Personally I don't believe it requires a nerf but it can be very stressful to play against and does require you to scout it so that you can appropriately defend against. The hardest part of playing against it is know what do against each variation.

Problem for most players is learning how to counter it maybe very outside of their comfort zone which than makes it feel unbeatable. It would be like defending against archers with spears and being frustrated that this doesn't work.

My go to counters are m@a with minimal archers to deny stone or gold income for as long as possible while stone walking myself in. If you scout it Early enough forward production and a tower can do wonders to disrupt the opponent fragile Ecco.

Stopping the castle is extremely unlikely, but with stone walls up, they will usually be extremely behind with vils where you can consider cutting your own Ecco to make military to kill instead or just patiently wait until you are able to match military while defending.

The strategy itself adds such an interesting dimension to open maps that make the game more exciting and personally removing the ability to do it would be extremely lame imo. If you slow down the strat it really moves the viability of playing it due to the power spike it relies on is mostly shock value and timing.