~bird princess~
Hi Neol! I run a Backstab build for PvE and dungeons, because like you I find it fun. 
I’ve been experimenting with different setups over the last few days for my traits: all of my other characters are kind of tanky-supporty, so I wanted my thief to have BIG NUMBERS but I also didn’t want to fall over at any given time. For gear I’ve been running a mix of (mostly) Berserker’s and (some) Valkyrie’s, with Beryl Orbs/Exquisite Beryl Jewels. I have 40% crit chance — 45% with my Sigil of Accuracy and 50% if I choose to equip Signet of Agility. Backstab, however, always crits since I use Hidden Killer.
The two trait setups I’ve found most efficient are the standard 25/30/0/0/15: the Valk gear boosts your health enough you can still take a hit or two and dish out a powerful one in return. The other one I’m really fond of is 20/30/20. You lose a chunk of damage compared to 25/30, but taking Shadow’s Embrace and Infusion of Shadow means every time you C&D, Hide in Shadows or Shadow Refuge you not only drop a condition, but gain two initiative. You also get a bunch of bonus Toughness.
25/30/15 is also an option but I’m not sure if that gives any advantage over 0/0/15. Taking Shadow’s Embrace gives you excellent condition management but initiative can be a bit dicey, and taking Infusion of Shadow means initiative is stellar but there’s no real reason to take that trait over Thrill of the Crime or Flanking Strikes.
Try some things out, see how you like them. I’ve found 20/30/20 surprisingly resilient in dungeons but I like big Backstabs so much I usually swap between builds if I’m going to a condition-heavy dungeon or not. Hope this helps!
~bird princess~
~bird princess~