I have some of the same questions. It occurs to me that without the Rebellion rebirth, that the original Gunslinger class is useless on pre-renewal servers where rebirthing for the original classes are available. There's basically nothing that a Gunslinger can do that a Hunter can't. And there's tons of things a Sniper can do that a Gunslinger can't.
I just don't see a regular Gunslinger competing in that kind of environment unless the server implements some VERY heavy customs (like extra HP pool, extra stats, and special or modified gears). Rebellion was a much needed update that brought the class more in line with the rest. Without Rebellion, plain Gunslinger seems like just another joke class and not really viable in endgame content like MVP/WOE/PVP. The stats and gear just aren't there, and the kit is weak.