Kind of funny that I keep hearing about the alleged operative "stunlock". People do realize that they only have one real stun that lasts for 4 seconds, right? And that snipers have that exact same stun? Sure, ops have that 1.5 second knockdown, so that time should be factored in as well, yet, however, again people do realize that assassins have the same thing too? The same knock down duration and a 4-second stun? Oh yes, and deception assassins also get that other stun with low slash. Yet no one ever talks about assassins "stunlocking" people to death. Don't get me wrong, I love my assassin, I'm just saying that yes, they are class a that's a real threat and can hold their own. Op/scoundrel though...they aren't anywhere near as scary as people make them sound. I'm tired of hearing all about how they can stunlock people to death making it sound as if they had more stuns than any other class which simply isn't true. If your an op/scoundrel you better hope your opponent is majorly undergeared or suffers from terrible lag.
I think that the Stunlock terminology comes from the pre 1.1 days of Scrappers, back when the Shoot First knockdown was 3 seconds. I remember back then when you hit a target for a 3 second knockdown, waited a moment for resolve to drop, kicked them for 4, and then popped Disappearing Act to get yet another Shoot First into yet another 3 second knockdown. Now that was a stunlock.
These days, the term is just meaningless, as you rightly point out. I do know that some players get annoyed by the 30s CD on Dirty Kick, and they feel as if they are always being stunned for 5.5 seconds every time that same annoying Op/Scrap jumps them. But those players are also inexperienced, undergeared, and/or just plain bad. Our stunlock is basically identical to that of a Sin/Shadow. Our kick has a 30s CD. Their 4s stun has a 50s (or 60s) CD. Spike is a 2s stun with a 30s CD. Shoot First is a 1.5s stun that can only be used from stealth. When you average those out over the course of a fight, Sins/Shadows really have the same stunning capabilities as we do.