1. Only useful in a duel if you open with a sap, or an insta-ww when they have no dots on them(lolwtf?)
2. Holy ****, really?!?!
3/4, No. PTs, Mercs, Jugs, other sins, operatives, snipers and marauders all have a way to avoid your instant re-sap. Sorcs also have a second breaker. Each class needs a different tactic to sap, if they play it right.
5. Dot spreading isnt the be-all and end-all of pvp, sometimes a dot can do more harm than good, your dot can easily ruin a lift thats being cast, or about to be cast on someone who it is more useful to keep out of the fight than it is to have two dots on. Only sometimes mind, but your "always do this" is bad advice.