I started my sin right when factions came out... I was frustrated with the PUG's not accepting sins, and went ahead and created a rit and went though the game... I since then have returned to my assassin to continue to work on him, because I knew it wasn't my fault I couldn't get into PUG's. My sin was left at the entrance to the mainland of cantha, where Sin hate is rampent, all of the noob sins made it off the first island, and got stuck trying to battle the afflicted.
Henchies it was...
Once I got past the first few missions, and over to the Temple, sin hate seemed distinctivly less rampent. I found alot of monks actually inviting me to their group, because they knew how bad sin hate was... so this is my story mind you, I was forced to hench through the first few mainland missions, and if things are the same as they were then, you probably will too. It's alot ezier then people realize, because of one simple stroke of 3 different keys(and that was a more complex way of making a very simple statment

)
A secret keystroke for henchies!?! WHAT... YES! Control+Shift+Space! It calls a target WITHOUT you automatically attacking

. This simple stroke of keys sends your henchies in FIRST, drawing all the aggro, and now, all you have to do is leap into the frey and start doing what the sin does best, systimatic elimination of crutial targets of a group
Once you have made it to the temple, I think people start to realize that you have to know what your doing to survive(unless you got ran, you cheap bastards!) because you wouldn't be that far if you didn't. I found life gets even ezier as you make your way into the jade sea and the echovald to find groups.
Mind you its still hard for a sin to get into the Deep and Urgoz's, because a sin's a hard class to play, and those are incredibly hard missions, but for the main story line, it seems as though sins are starting to get some credit, be it small, for what they do.
I hope that gives you some idea of what you might face playing a sin, but it does kinda make sense that an assassin is a hard group to be accepted(im sure they were never looked upon in the highest standards IRL) but there seems to be a growing trend, especially when you start getting to areas where people realize its not one player's fault a team failed(usually, case and point LEEEEROOOY JENKINS!) but that there was somthing that your group didn't prepare for... Good luck, and happy Sinning