Do you know how many Pokemon learn Roar? Tons. Many of which can easily OHKO both a Smasher and an Espeon. Just because the few most common ones may not be able to dosesn't mean they don't exist. Arcanine, Rhyperior, Mamoswine, Houndoom, Drapion, etc. all can both phaze and KO. Espeon can't switch in freely if it is going to be KOd.
And even if you can't OHKO, just doing big damage is good enough. There is such thing as priority for finishing things off.
Your forgetting the most IMPORTANT fact...the smash passer...gorebyss/huntail vs. the pokes you named...they can just easily KO all of them with ease hahaha..ppl arent stupid..if I see a rhyperior switch into my gorebyss right when i smash..you damn right im going for that KO..AGAIN!! ppl arent just switching espeon on BP teams in for the fun of it.