For sure, it is entirely possible to solo PVP as a Gunslinger, as I did quite a bit of it myself even before the bracket split. But the truth of the matter is this: it takes much more tactical planning to be successful as a Gunslinger, as you will have to know the best cover spots for any given WZ, and understand the essence of tactically superior cover positions for Open-World PVP.
Also, as a Gunslinger, you will be targeted by certain types of players and classes as you really are an easy kill. Lack of survivability and ability to return damage while on the run makes you a likely target for classes looking for a quick medal. I should know, as on my Scoundrel, I usually quickly dispatch any Snipers present on the field if I don't see any healers.
The good thing about a Scoundrel is that you can choose when to tip your hand, whereas for the Gunslinger, the hand is tipped against you from the beginning. I will not deny, however, the excitement that can be had by successfully locking down a node in Alderaan or a bridge in Voidstar with a Gunslinger. Alot of fun can be had.
I suppose a good way of coming to a conclusion would be to consider what you have enjoyed in the past. If you played or would like to play a WoW rogue that also has the ability to heal, go Scoundrel. If you played or would like to a play a WoW Mage with a bit less relative damage and the potential to lose alot of mobility, go Gunslinger.
Well, that doesn't make it sound very good, does it?