I was obviously wrong about Immolation Trap, and I acknowledge that.
When I'm on my own at least, however, damage isn't actually my main priority.
It might be in an instance, yes; but as I wrote a few posts ago, for a bit before the release of 3.1, for farming I actually specced *out* of ES/L&L because I got bored with running around one shotting everything that moves.
If I'm still trapping, I can farm for hours and not get bored. With ES, though, I find my eyes starting to glaze over after only the first few mobs; as you say, it sucks.
Seriously; use dual speccing and, as a farming spec, give yourself this.
Then you can switch between that and the ES/L&L/BA whack-a-mole spec to use in Heroics or raids.
It's essentially what we had during TBC, but with the Glyph of Immolation Trap, CA, and Hunting Party as well. I'd never use this in a Heroic or raid of course; but when I'm alone, I can choose what's actually fun to play, not what's purely high DPS.
If I could spec for ES without Black Arrow I would, but unfortunately we're not given that choice.