Hmh, to answer some stuff -
No, it's not common sense. You can't normally sap targets in combat.
Yes, it works.
No, no lag required.
No, the timing is not really that hard.
About the stunlocking, a stunlock + nuke is a common tactic. Infact, this is how rogue and mage should work, timing shattercombos with stuns. I tought the poster meant saplocking.
But yeah, you can do the saptrick twice and proceed to normal stunlock.