After testing hail somewhat extensively, I can say that one point being neglected by the above post is that Smoochum is a hail sweeper whereas Abra is something pretty different. The name of the game is Blizzspam, which provides important coverage with Psyshock or Psychic (Psychic's better overall since Timburr has higher Defense than Special Defense [Mienfoo possesses equal defensive stats] but the Nasty Plot set can't afford being walled so Psyshock sees use there). Hate to break it to ya, but Ferroseed does not wall Substitute Smoochum. Try taking a few Blizzards then get back to me...
In any case, Ferroseed is a good example of how to play this set. Let's take a look why.
I send out Smoochum to revenge, let's say, Natu, at an opportune moment early game. There's not a whole lot Smoochum can force out; then again, there's not that much Drilbur yet to set up can force out either. I Substitute, and Ferroseed, seeming like a decent switch-in to the average passerby (as Methmite so casually demonstrated) comes in on the opponent's team. I go for a Blizzard, crippling it greatly while it a.) breaks my sub or b.) sets up hazards predicting a switch. If a.) the user is greatly concerned as to losing Ferroseed, a Poke who's only recovery is Leech Seed early game, and I can sub again hoping they switch and worse case just lose 25% more on a fragile mon. If b.) they're really in trouble. Either way, what my opponent just thought of as their best answer to Smoochum is now in trouble, and if I keep my sub up, priority is not a worry. Actually, Protect can even merit a spot on this set instead of Nasty Plot if you are afraid of Mienfoo / Croagunk.
Either way, the set's not "lol completely outclassed," it's just an alternative to Scarf Smoochum, that if bluffed correctly, can cause trouble for the opponent.