The only bullshit EMMI is the purple one, the first encounter with it is a stupid game of trial and error and you can barely move underwater and it detects you immediately when uncloaked. Previous EMMIs taught you that if you were dexterous, you didn't need the cloak and/or could bait the enemy away and make a run for it. That time it's almost pure trial and error until you figure it out, that's not good gameplay.
But I do think that they don't add much to the game. Two of three of them would have been enough, not six.