In the past 6 months I tryed a more or less defensive shadow build and it worked fine so far, most of the time in the top 10 (expect some abysmal placings during skill changes, if you wanna change skills grab those free 200 skillpoints at the lower ranks!!)

Lets call it a "Drain Shadow" build and in my opinion its a very viable build. I hope that 6 months are enough to call them safely a viable build for BG.

As it turned out, the most successful build was a mixed build with a 60/40 win ratio (drain/damage).
The 2 most used weapons are tridents in (offense and defense) and nets mostly for defense.

The second best was a high defensive build with lots of "Defense" from equipment and dropping "dual strike" for another passiv skill. Sadly that build is very weak against trixsters (cheating bastards) which are always lurking in the top spots and ultimately spoil the last week of the season with many defeats....

There are basically two sets of strategies for the howl season. Either you tune your strats against all but trixsters or you dedicate all your 5 slots for trixsters and hope for the best.
I know it would be wise to have at least 3 sets of strategies, 1 basic for the first 2 weeks and 2 other depending on the current 20 glads around yours.

Long story short, a defensive shadow build is viable and able to win a season. Now its time to dive into a more violent build and go full offense.

I will try to update this thread with more "viable" builds and hopefully some exotic unexpected variants. As for now the next update should be about offense