It's not quite that good because it comes at the opportunity cost of +2 Con. Toughness isn't +2 hp/level, it's +1 hp/level over the existing ASI. I'd rather have +1 to Con saves and checks than +4 hit points. If we say that the average hit from an average creature deals 8 damage, then it takes Toughnesss 8 levels to increase survivability by one additional hit over +2 Con.
A fair point..but it becomes mute if someone has a 20 con. And maybe that's toughness' niche, but it's still very strong in that niche.