You need to read LITERALLY.
"Creatures entering in the battlefield don't cause abilities to trigger" = Abilities triggered by a ETB (
Entering
The
Battlefield) don't trigger.
I have a deck with this combo too (and other creatures with similar negative-effects) plus things like Trickbind (Split second and counter triggered ability = if you destroy torpor in response to a creature, i allow entering creature but in response counter negative triggered ability). BTW Allys decks are insta-destroyed with a torpor in game. I have to admit sometimes i have doubts too, last time I played my deck with Guttersnipe vs my deck with torpor and don't remembered Torpor only affects ETB triggers so i winned without apply Guttersnipe effects.
In things like "you cast/play" like Emrakul the best you can do is is read careful:
* "play" means play succesful so you need to play the spell and next the ability triggers if conditions are OK. For example Eater Of Days says "when you play [...] skip two turns" so when the creature enters this trigger go to pile the two-turns-skip-effect (if Eater is countered, this ability don't trigger).
* "cast" means just cast. If one effect trigger when you cast, go to pile (over your spell so resolve before the spell you casted) and this triggered effect don't cancel if the spell(s) are countered. If emrakul is played from your hand, you have a extra turn before this creature ETB or is countered (in this example, can't be countered but is the same).
One example of "abusing" this cast mechanic i like is
Livewire Lash he say: "Equipped creature gets +2/+0 and has "Whenever this creature becomes the target of a spell, this creature deals 2 damage to target creature or player."
Become target of a spell = become target of a cast.
* Opponent cast Lightning to this creature.
* You in response cast a instant with hexproof to this creature.
The pile look like this:
* Two damage triggered effect
* Hexproof effect
* Two damage triggered effect
* Lightning effect
2 dmg, hexproof, 2 dmg, lightning canceled but the 2dmg provoked by lightning spell don't countered. And the best thing is the damage is done
by the creature (not by the equipment) so if the creature have extra abilitys that can trigger: lifelink for extra life, death touch for destroy creatures, wither for -1/-1 counters or infect (in a creature with infect is 100% bullying xD).[/...]