Let’s see…
1. It can screw with your opponent’s deathrattle minions.
2. It can get rid of a large / legendary minion that you can’t kill.
3. In most cases newly summoned minions will be weaker, for only 2 mana it is a good trade. You can even summon something like “Doomslayer” that will wipe the board.
4. Some decks require a particular minion/s to die (paladin murlocs) or be present on board (pirates synergy / elementals / dragons) so by devolving them you can screw with your opponents strategy.

Nefarian? Really? Not Deathwing? Cause being able to clear the field in late seems more useful 2 me than 2 random spells. Also better stats.

I dont think so, I’ve dropped frothing from my deck completely