In my experience, I've always been matched with players with the same GP as me (+/-2%), so i don't think anything more than GP has taken into account.
Well, I don't have Traya until now, it was my own choice, but I'm an officer, and I preferred to stay in my old, friendly and non-heroic STR guild and help the rest of my mates to beat the heroic instead of simply change the guild, and I believe that there are many people in the same situation out there.
I don't have Revan because... well I think its not necessary to explain why I don't have Revan....
It's fun to read that collecting and gearing as many toons as possible is useless in all game modes. Again, in my experience, it helped a lot and my guild when the TB arrived, and I do not see the need to explain the reason, it is quite obvious... On the other hand you can also unlock the legendary ones, some of them with the bare minimum, and the additional GP in TW helped a lot to overcome the 120M GP barrier.
Until GA I didn't see any problem with increasing your GP to help your guild, and Paywall Revan was only a problem in TW, but with a good strategy my guild can always get over it. But in GA there are no alternatives, if your opponent paid for a wall, ypu already lost.