There's no safe perfect way.. I find the infernal meteor stun to be useful in some cases.. Bit of a luxury blowing a 3 min cd to stop a cap.. Sometimes it's worth it though.
Other than that, as you said, pet, fear, meleeing..
I think procs from GoSac interrupts it, but normally you're not running that.. And it's still RNG at that point.
If you're sitting a base/trying to spin, you should be using Succubus. The Fel Lash knockback can be used first, then Succubus drops Invis, then use Seduction to buy time, then sit your pet on them and let the melee swings spin. If you're Affliction, you should probably be using Howl in RBGs. Easy multi-target flag spin, and can be alternated with Fel Lash. If I'm sitting a base, I'll never get capped on unless I get zerged by multiple stealthies and killed. Pet ability spins are crucial. Infernal stun should be a last resort, and anyone worth their salt will be CCing you while they cap.