What I really like about thieves is you can hide after combat. Assassins were not much of a problem for me. If they are tranced, don't waste your time. Thug is a good path w/cheapshot. Of course, the more you kill, the more they remember to fly. Also, steal is great when you need to negotiate an understanding with that build you just cannot seem to beat.

The only drawback to defender is stepping out of the shadows when you use your powers. Not so with scouts.

Also, though I used it very rarely, I liked separate. Great for necros.

Btw, you won't be soloing inners.

Gergan, Tummel, Heaghul, Ild